# Complementary and supplementary anglesÂ review

CCSS Math: 7.G.B.5
Review the basics of complementary and supplementary angles, and try some practice problems.

## Complementary angles

Complementary angles are two angles with a sum of $90 ^\circ$. A common case is when they form a right angle.
For example, $\angle BXC$ and $\angle CXD$ are complementary angles in the following diagram:
Note that $\angle BXD$ must be a right angle because $\angle AXB$ is a right angle.

## Supplementary angles

Supplementary angles are two angles with a sum of $180 ^\circ$. A common case is when they lie on the same side of a straight line.
For example, $\angle AXD$ and $\angle DXC$ are supplementary angles in the following diagram:

## Practice set 1: Identify complementary and supplementary angles

Problem 1A
What is the relationship between $\angle AXY$ and $\angle YXB$?
All segments that appear straight are straight.
If $\angle AOC$ is a right angle and $m \angle AOB = 79^\circ$, what is $m \angle BOC$?
$\Large{^\circ}$