Introduction:

In geometry, a quadrilateral is a four-sided polygon. To find the measure of the fourth angle of a quadrilateral, you need to know the measures of the other three angles.



Understanding Quadrilaterals:



A quadrilateral has four angles.

The sum of the interior angles in any quadrilateral is always 360 degrees.

Calculating the Fourth Angle:



To find the fourth angle, add the measures of the three known angles.

Subtract this sum from 360 degrees to find the measure of the fourth angle.

Example:



If the three known angles of a quadrilateral are 90 degrees, 80 degrees, and 100 degrees:

Add these angles: 90 + 80 + 100 = 270 degrees.

Subtract this sum from 360: 360 - 270 = 90 degrees.

The measure of the fourth angle is 90 degrees.

Key Points to Remember:



The total sum of angles in a quadrilateral is 360 degrees.

This method assumes the quadrilateral is a simple, closed figure with non-intersecting sides.