Interior angles of a polygon
Use the polygon interior-angle-sum formula (n - 2) * 180 to find a regular polygon's interior angle or a missing angle in an irregular polygon. Unlimited questions, five difficulty levels, and a full worked solution every time — free.
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A regular triangle has 3 sides. What is the sum of its interior angles?
Answer: 180
See one solved, step by step
The interior angles of a 4-sided polygon measure 79 deg, 39 deg, 144 deg, and x. Find the value of x.
📘 Worked solution
1Sum of interior angles = (n - 2) · 180 = (4 - 2) · 180 = 360°Any polygon's interior angles sum to (number of sides − 2) × 180 deg.
2Known angles add to 79 + 39 + 144 = 262°Add up all the angles you already know.
3x = 360 - 262 = 98°The unknown angle makes up the rest of the total.
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