# EC geometry: chap. 2 & 3 theorems

## 18 terms

### Properties of Segment Congruence

Segment congruence is reflexive, symmetric, and transitive.

### Properties of Angle Congruence

Angle congruence is reflexive, symmetric, and transitive

### Right angle congruence theorem

All right angles are congruent

### Congruent supplements theorem

if two angles are supplementary to the same angle (or to congruent angles) then they are congruent

### Congruent complements theorem

If two angles are complementary to the same angle (or congruent angles) then the two angles are congruent

### Vertical angles theorem

Vertical angles are congruent

### 3.1

If two lines intersect to form a linear pair of congruent angles, then the lines are perpendicular

### 3.2

If two sides of two adjacent acute angles are perpendicular, then the angles are complementary

### 3.3

If two lines are perpendicular, then they intersect to form 4 right angles

### Alternate interior angles

If two parallel lines are cut by a transversal, then the pairs of alternate interior angles are congruent

### Consecutive interior angles

If two parallel lines are cut by a transversal, then the pairs of consecutive interior angles are supplementary

### Alternate exterior angles

If two parallel lines are cut by a transversal, then the pairs of alternate exterior angles are congruent

### Perpendicular Transversal

If a transversal is perpendicular to one of the two parallel lines, then it is perpendicular to the other

### Alternate interior angles converse

If two lines are cut by a transversal so that alternate interior angles are congruent, then the lines are parallel

### Consecutive interior angles converse

If two lines are cut by a transversal so that consecutive interior angles are supplementary, then the lines are parallel

### Alternate exterior angles converse

If two lines are cut by a transversal so that alternate exterior angles are congruent, then the lines are parallel

### 3.11

If two lines are parallel to the same line, then they are parallel to each other

### 3.12

In a plane, if two lines are perpendicular to the same line, then they are parallel to each other

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