## Angle Addition Postulate

Help and definitions

First some definitions.

__Adjacent__ angles share a common side. Imagine holding one page of a book
up. The front cover and the page make one angle. The page and the
back cover make a second angle that is ADJACENT to the first angle.

An ** acute** angle is less than 90 degrees.

An __ obtuse__ angle is more than 90 degrees.

A __ right__ angle measures exactly 90 degrees.

A __ straight__ angle measures 180 degrees (and is really a straight line)

__Complementary__ angles may or may not be adjacent but together they always add
up to 90 degrees.

__
Supplementary__ angles may or may not be adjacent but together they always add up
to 180 degrees.

A __ __**line**ar pair is a pair of adjacent angles that are supplementary (which
means together they form a straight **line**).

Example:

Angle 1 and angle 2 are linear pairs. Angle 2 measures 6 more than 5 times
the measure of angle 1. How big is angle 2 and what is its type?

So angle 1 and 2 add to 180, because that's what linear pairs must do since
the form a straight line.

Let angle 1 = x

angle 2 = 6 + 5x

x + 6 + 5x = 180

6 + 6x = 180

6x = 174

x = 29 (this is angle 1, but the question asked about
angle 2)

Angle 2 = 6 + 5(29)

So angle 2 is 151 and is obtuse.

CHECK YOURSELF.

Does 151 + 29 equal 180? (Yes)

Is 151 six more than five times 29? (Yes)