| Question | Answer | Question | Answer |
| acute angle | angle less than 90 degrees | | |
| obtuse angle | angle greater than 90 degrees | | |
| right angle | angle equaling 90 degrees | | |
| acute triangle | triangle with all acute angles | | |
| obtuse triangle | triangle with one obtuse angle | | |
| right triangle | triangle with one right angle | | |
| scalene triangle | triangles whose sides are all different measures | | |
| isosceles triangle | triangle with two sides that are congruent | | |
| equilateral triangle | triangle with all three sides congruent | | |
| equiangular triangle | triangle with three congruent angles | | |
| The measure of an angle in an equilateral or equiangular triangle | 60 degrees | | |
| The sum of all angles in a triangle | 180 degrees | | |
| exterior angle of a triangle | angle formed by one side of a triangle and the extension of another side | | |
| remote interior angles | interior angles not adjacent to a given exterior angle | | |
| congruent triangles | triangles that have corresponding parts congruent | | |
| congruence transformations | occurs when a slide | flip | or turn of a triangle does not change the size or shape |
| included angle | angle formed by two sides of a triangle | | |
| SSS Postulate | If the sides of one triangle are congruent to the sides of another triangle | then the two triangles are congruent. | |
| SAS Postulate | If two sides of a triangle and their included angle are congruent to two sides of another triangles and their included angle | then the triangles are congruent. | |
| included side | the side between two angles of a triangle | | |
| ASA Postulate | If two angles and the included side of one triangle are congruent to two angles and the included side of another triangle | then the two triangles are congruent. | |
| AAS Postulate | If two angles and a nonincluded side of one triangle are congruent to the corresponding angles and side of a second triangle | then the two triangles are congruent. | |
| SSA Postulate | a valid test of congruence for right triangles | | |
| base angles | two angles formed by the base and the congruent sides of an isosceles triangle | | |
| vertex angle | angle formed by the two congruent sides of an isosceles triangle | | |
| coordinate proof | uses figures in the coordinate plane and algebra to prove geometric concepts | | |
