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