### As student many times, you are confronted with having to complete proofs, and you think: How do I start completing the proof? Or you just find difficult to understand the proofs that your teacher, or the textbook present to you.

### In this lesson, you will be given several examples that use colors and sequence to highlight each one of the steps in the corresponding proof; then you are shown the same proof with different labels to order the reasons. You will find it challenging while having some fun! Don't miss the opportunity to take advantage of interacting with the lesson solving the suggested problems using your stylus and the marker tools menu.

** Lesson's Content **

** Lesson's Glossary **

**Alternate exterior angles **

Exterior angles on alternate sides of the transversal (not on the same parallel line)

** Alternate interior angles **

Interior angles on alternate sides of the transversal (not on the same parallel line)

** Complementary angles **

Two positive angles that when added give 90 degrees.

**Corresponding angles **

Any pair of angles in similar locations with respect to a transversal.

**Linear pair **

2 supplementary adjacent angles whose non-common sides form a line.

**Parallel lines **

Two or more coplanar lines that never intersect.

**Perpendicular lines **

Two segments, rays, or lines that form a 90 degree angle.

**Postulate **

A statement assumed to be true without proof.

**Proof **

A sequence of justified conclusions used to prove the validity of an if-then statement.

**Supplementary angles **

Two positive angles whose measures add to 180 degrees.

**Theorem**

A theorem in mathematics is a proven fact. A theorem about polygon must be true for every polygon; there can be no exceptions. An idea which works in several different cases is not enough.

**Transversal **

A line that intersects others.

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