FlashKeepers

Math · High School

Geometry Proofs and Theorems

Classic geometry theorems, postulates, and two-column proof structure for a high school geometry course.

39 cards · basic cards · AI-written, checked twice. Edit anything.

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Define a postulate in geometry.
A statement assumed to be true without proof.
Define a theorem in geometry.
A statement that is proven true using postulates and other theorems.
State the Vertical Angles Theorem.
Vertical angles are congruent.
What is the sum of complementary angles?
90 degrees.
What is the sum of supplementary angles?
180 degrees.
What is the SSS congruence criterion for triangles?
If all three sides of one triangle are congruent to the three sides of another triangle, the triangles are congruent.
What is the SAS congruence criterion for triangles?
If two sides and the included angle of one triangle are congruent to two sides and the included angle of another triangle, the triangles are congruent.
What is the ASA congruence criterion for triangles?
If two angles and the included side of one triangle are congruent to two angles and the included side of another triangle, the triangles are congruent.
What is the AAS congruence criterion for triangles?
If two angles and a non-included side of one triangle are congruent to two angles and the corresponding non-included side of another triangle, the triangles are congruent.
What is the HL congruence criterion for right triangles?
If the hypotenuse and one leg of a right triangle are congruent to the hypotenuse and one leg of another right triangle, the triangles are congruent.
State the Isosceles Triangle Theorem.
If two sides of a triangle are congruent, then the angles opposite those sides are congruent.
What is the sum of the interior angles of a triangle?
180 degrees.
State the Exterior Angle Theorem.
An exterior angle of a triangle equals the sum of the two non-adjacent interior angles.
Define the Angle Bisector Theorem.
An angle bisector of a triangle divides the opposite side into segments proportional to the other two sides.
State the AA similarity criterion for triangles.
If two angles of one triangle are congruent to two angles of another triangle, the triangles are similar.

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