Geometry postulates, theorems, corollary, properties – Flashcards
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            Properties of kites
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        Perpendicular diagonals, one pair of congruent opposite angles
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            Isoceles trapezoids theorem
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        Each pair of base angles are congruent, if and only if diagonals are congruent
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            Conditional statement
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        If p, then q
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            Hypothesis
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        If p part of conditional statement
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            Conclusion
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        Then q part of conditional statement
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            Converse of conditional
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        Exchange hypothesis and conclusion q-p
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            Inverse of conditional
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        Negating hypothesis and conclusion ~p-~q
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            Contrapositive of conditional
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        Exchanging and negating hypothesis and conclusion
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            Biconditional statement
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        P if and only if q
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            Addition property of equality
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        If a=b, then a+c=b+c
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            Subtraction property of equality
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        If a=b, then a-c=b-c
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            Multiplication property of equality
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        If a=b, then ac=ab
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            Division property of equality
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        If a=b, then a/c=b/c
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            Reflexive property of equality
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        a=a
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            Symmetric property of equality
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        If a=b then b=a
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            Transitive property of equality
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        If a=b and b=c, then a=c
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            Substitution property of equality
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        If a=b, then b can be substituted for a in any expression
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            Reflexive property of congruence
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        Figure A ≅ figure A
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            Symmetric property of congruence
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        If figure A ≅ figure B, then figure B ≅ figure A
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            Transitive property of congruence
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        If figure A ≅ figure B and figure B ≅ figure C, then figure A ≅ figure C
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            Linear pair theorem
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        If two angles form a linear pair, then they are supplementary
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            Congruent supplements theorem
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        If two angles are supplementary to the same angle, then the two angles are congruent
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            Right angle congruence theorem
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        All right angles are congruent
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            Congruent complements theorem
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        If two angles are complementary to the same angle, then the two angles are congruent
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            Common segments theorem
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        If ab ≅ cd, then ac ≅ bd
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            Corresponding angles postulate
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        If two parallel lines are cut by a transversal, then the pairs of corresponding angles are congruent
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            Reflexive property of equality
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        a=a
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            Symmetric property of equality
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        If a=b then b=a
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            Transitive property of equality
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        If a=b and b=c, then a=c
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            Substitution property of equality
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        If a=b, then b can be substituted for a in any expression
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            Reflexive property of congruence
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        Figure A ≅ figure A
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            Symmetric property of congruence
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        If figure A ≅ figure B, then figure B ≅ figure A
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            Transitive property of congruence
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        If figure A ≅ figure B and figure B ≅ figure C, then figure A ≅ figure C
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            Linear pair theorem
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        If two angles form a linear pair, then they are supplementary
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            Congruent supplements theorem
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        If two angles are supplementary to the same angle, then the two angles are congruent
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            Right angle congruence theorem
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        All right angles are congruent
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            Congruent complements theorem
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        If two angles are complementary to the same angle, then the two angles are congruent
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            Common segments theorem
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        If ab ≅ cd, then ac ≅ bd
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            Corresponding angles postulate
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        If two parallel lines are cut by a transversal, then the pairs of corresponding angles are congruent
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            Vertical angles theorem
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        Vertical angles are congruent
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            Congruent supplements theorem
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        If two congruent angles are supplementary, then each angle is a right angle
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            Conjunction
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        Compound statement that uses "and"
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            Disjunction
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        Compound statement that uses "or"
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            Skew lines
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        Not coplanar, parallel, or intersecting
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            Transversal
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        Line that intersects two coplanar lines at two different points
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            Alternate interior angles theorem
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        If two parallel lines are cut by a transversal, then the pairs of alternate interior angles are congruent
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            Alternate exterior angles theorem
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        If two parallel lines are cut by a transversal, then the two pairs of alternate exterior angles are congruent
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            Same-side interior angles theorem
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        If two parallel lines are cut by a transversal, then the two pairs of same-side interior angles are supplementary
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            Converse of corresponding angles postulate
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        If two coplanar lines are cut by a transversal so that a pair of corresponding angles are congruent, then the two lines are parallel
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            Parallel postulate
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        Through a line p not on line l, there is exactly one line parallel to line l
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            Converse of alternate interior angles theorem
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        If two coplanar lines are cut by a transversal so that a pair of alternate interior angles are congruent, then the two lines are parallel
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            Converse of alternate exterior angles theorem
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        If two coplanar lines are cut by a transversal so that a pair of alternate exterior angles are congruent, then the two lines are parallel
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            Converse of the same-side interior angles theorem
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        If two coplanar lines are cut by a transversal so that a pair of same-side interior angles are supplementary, then the two lines are parallel
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            Perpendicular congruent angles theorem
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        If two intersecting lines form a linear pair of congruent angles, then the lines are perpendicular
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            Perpendicular transversal theorem
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        If a transversal is perpendicular to one of the two parallel lines, then it is perpendicular to the other line
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            Perpendicular lines theorem
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        If two coplanar lines are perpendicular to the same line, then the two lines are parallel to each other
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            Point-slope form
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        Y-y1=m (x-x1)
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            Slope-intercept form
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        Y=mx+b
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            Triangle classification by angles
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        Acute, equiangular, right, obtuse
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            Triangle classification by side length
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        Equilateral, isoceles, scalene
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            Exterior angle theorem
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        The measure of an exterior angle of a triangle is equal to the sum of its remote interior angles
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            SSS congruence postulate
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        If three sides of a triangle are congruent to three sides of another triangle, then the triangles are congruent
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            SAS congruence postulate
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        If two sides and the included angle of one triangle are congruent to two sides and the included angle of another triangle, then the two triangles are congruent
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            ASA congruence postulate
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        If two angles and the included side of one triangle are congruent to two angles and the included side of another triangle, then the triangles are congruent
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            AAS congruence theorem
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        If two angles and a nonincluded side of one triangle are congruent to the corresponding angles and nonincluded side of another triangle, then the triangles are congruent
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            HL congruence theorem
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        If the hypotenuse and a leg of a right triangle are congruent to the hypotenuse and a leg of another right triangle, then the triangles are congruent
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            CPCTC
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        corresponding parts of congruent triangles are congruent
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            Perpendicular bisector theorem
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        If a point is on the perpendicular bisector of a segment, then it is equidistant from the endpoints of the segment
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            Converse of the perpendicular bisector theorem
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        If a point is equidistant from the endpoints of a segment, then it is on the perpendicular bisector of the segment
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            Angle bisector theorem
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        If a point is on the bisector of an angle, then it is equidistant from the sides of the angle
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            Converse of the angle bisector theorem
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        If a point in the interior of an angle is equidistant from the sides of the angle, then it is on the bisector of the angle
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            Circumcenter of a triangle
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        Point where the three perpendicular bisectors intersect inside or outside
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            Circumcenter theorem
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        The circumcenter of a triangle is equidistant from the vertices of the triangle
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            Incenter of a triangle
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        Point where the three angle bisectors intersect always inside
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            Incenter theorem
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        The Incenter of a triangle is equidistant from the sides of the triangle
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            Median of a triangle
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        A segment whose endpoints are a vertex of the triangle and the midpoint of the opposite side
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            Centroid of a triangle
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        Point where the three medians intersect; center of gravity
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            Centroid theorem
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        The centroid of a triangle is located 2/3 of the distance from each vertex to the midpoint of the opposite side
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            Altitude of a triangle
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        A perpendicular segment from a vertex to the line containing the opposite side
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            Orthocenter of the triangle
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        When the three altitudes of a triangle intersect inside or outside
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            Midsegment of a triangle
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        A segment that joins the midpoints of two sides of the triangle; three midsegments form midsegment triangle
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            Triangle midsegment theorem
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        A midsegment of a triangle is parallel to a side of the triangle, and its length is half the length of that side
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            Angle-side relationships in triangles
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        The larger angle is opposite the longer side
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            Pythagorean inequalities theorem
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        If c^2 > a^2 + b^2, then it is an obtuse triangle. If less, then acute
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            45-45-90
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        X,x,x root 2
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            30-60-90
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        X,x root 3,2x
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            Properties of parallelograms
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        Diagonals bisect each other
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            Properties of rhombuses
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        Diagonals are perpendicular and bisect opposite angles
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            Properties of kites
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        Diagonals are perpendicular and one pair of congruent opposite angles
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            Isoceles trapezoids theorems
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        Congruent base angles
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            Trapezoid midsegment theorem
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        The midsegment of a trapezoid is parallel to each base and its length is half the sum of the bases
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            AA similarity theorem
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        Two congruent angles on another triangle
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            SSS similarity theorem
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        Proportional sides
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            SAS similarity theorem
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        Two sides proportional and included angle congruent
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            Triangle proportionality theorem
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        If a line parallel to one side of a triangle intersects the other two sides, then it divides those sides proportionally
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            Two traversal proportionality corollary
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        If three or more parallel lines intersect two transversals, then they divide the transversals proportionally
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            Triangle angle bisector theorem
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        An angle bisector of a triangle divides the opposite side into two segments whose lengths are proportional to the lengths of the other two sides
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            Geometric means corollaries
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        The altitude/height to the hypotenuse of a right triangle is the geometric mean of the lengths of the two segments of the hypotenuse. The length of a leg of a right triangle is the geometric mean of the lengths of the hypotenuse and the segment of the hypotenuse adjacent to that leg
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            Sine,cosine,tangent
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        Aghaghagh
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            Law of sines
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        SinA/a=sinB/b=sinC/c
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            Law of cosines
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        a^2=b^2+c^2-bccosA
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            Geometric mean
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        Square root of product