# terms, theorems, postulates

### 25 terms by wendymckain

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concepts of basic geometry

### parallel

coplanar lines that do not intersect; everywhere equidistant

### perpendicular

intersecting at 90 degree angles

### vertical angle theorem

Vertical angles are congruent

### linear pair

two supplementary adjacent angles; opposite rays form a straight line

### corresponding angles postulate

if // lines are crossed by a transversal, corresponding angles are congruent

### alternate interior angles theorem

if // lines are crossed by a transversal, alternate interior angles are congruent

### same side interior angle theorem

if // lines are crossed bya transversal, same side interior angles are supplementary

### triangle sum theorem

the sum of the angles in a triangle is 180

### Isosceles triangle theorem

the base angles of an isosceles triangle are congruent

AB = AB

### transitive property

if A = B and B =C, then A = C

AB = BA

### converse of Isosceles triangle theorem

If 2 angles in a triangle are congruent, then the sides opposite those angles are also congruent

### 180(n-2)

Sum of the degrees of a polygon with 'n' sides

### angle bisector

line, segment, or ray that splits an angle into two equal angles

### perpendicular bisector

line, segment or ray that intersects a segment at its midpoint at a 90 degree angle

### midpoint

point on a segment exactly halfway between the endpoints

### HL theorem

If the hypotenuse and one of the legs of a right triangle are congruent to the hypotenuse and one of the legs of another right triangle, then the triangles are congruent

### SSS

If 3 sides of one triangle are congruent to 3 sides of another, then the triangles are congruent

### SAS

If two sides and the INCLUDED angle of one triangle are congruent to two sides and the INCLUDED angle of another, then the triangles are congruent

### ASA

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

### AAS

If any two angles and one side of a triangle are congruent to two angles and a side of another triangle, then the triangles are congruent

### vertex of isosceles triangle

angle formed by the two congruent legs

### base angles

angles opposite the two congruent legs of an isosceles triangle

### hypotenuse

longest side of a right triangle; opposite the right angle

Example: