The sum of interior angles in a quadrilateral is 360°. This fact is a more specific example of the equation for calculating the sum of the interior angles of a polygon: \(\text {Sum of interior ...

First, find the sum of the interior angles using the formula: (𝒏 – 2) × 180 = (8 – 2) × 180 = 6 × 180 = 1080. Then divide this by the number of sides, eight: 1080 divided by 8 = 135.