Question

Write a rule to find the sum of interior angles for any polygon:

Exercise: Using the rule above, find the sum of interior angles of the given polygon
1. A quadrilateral
2
A pentagon
3. An octagon
4. A polygon with 11 sides
5. A polygon with 15 sides

Answer 1

quadrilateral: (4-2)*180=360

pentagon：(5-2)*180=540

octagon: 6*180=540

11 sides: 9*180=1620

15 sides; 13*180=2340

Explanation:

a n sides convex polygon has Sum of interior angle

S = ( n −2) × 180°

quadrilateral: (4-2)*180=360

pentagon：(5-2)*180=540

octagon: 6*180=540

11 sides: 9*180=1620

15 sides; 13*180=2340