### Contrapositive

The equivalent statement formed by negating the hypothesis and conclusion of the converse of a conditional statement.

### Counterexample

A specific case that proves a conjecture/statement false. All it takes is one to prove a conjecture false.

### Converse

The statement formed by exchanging the hypothesis and conclusion of a conditional statement.

### Deductive Reasoning

A process that uses facts, definitions, accepted properties, and the laws of logic to form a logical argument.

### Perpendicular Lines

Two lines that intersect to form a right angle. Their slopes are opposite reciprocals of each other.

### Corresponding Angles

Two angles that are formed by two lines and a transversal and occupy corresponding positions

### Consecutive Interior Angles

Two angles that are formed by two lines and a transversal and lie between the two lines and on the same side of the transversal.

### Alternate Interior Angles

Two angles that are formed by two lines and a transversal and lie between the two lines and on opposite sides of the transversal.

### Alternate Exterior Angles

Two angles that are formed by two lines and a transversal and lie outside the two lines and on opposite sides of the transversal.