Find missing angles in triangles and quadrilaterals
Key Notes:
The sum of the angles in a triangle is always 180°.
Learn with an example
What is the measure of the missing angle?—–
The sum of the three angles must be 180°. The two angles you know measure 130° and 25°.
Write an equation and find the measure of the unknown angle.
130° +25°+?=180°
155°+?=180°
?=180°-155°
?=25°
The measure of the missing angle is 25°.
What is the measure of the missing angle?
The sum of the four angles must be 360°. The three angles you know measure 61°, 84°, and 123°.
Write an equation and find the measure of the unknown angle.
61° +84°+123°+?=360°
268°+?=360°
?=360°-268°
?=92°
The measure of the missing angle is 92°.
What is the measure of the missing angle?
The sum of the four angles must be 360°. The three angles you know measure 84°, 146°, and 63°.
Write an equation and find the measure of the unknown angle.
84° +146°+63°+?=360°
293°+?=360°
?=360°-293°
?=67°
The measure of the missing angle is 67°.
let’s practice!
