Answer:
area = 289.24 units²
Step-by-step explanation:
divide the polygon into 9 equal triangles
the top angle of a triangle will be 360°/9 = 40°
the sides of a triangles are both 10 units
The base of a triangle is 6.84 units
the height of a triangle is:
cos 20° = height/10
0.9397 = height/10
height = 9.4 units
The area of a triangle = 1/2(6.84)(9.4) = 32.13 units²
the polygon is made from 9 of these triangles, so 9 x 32.13 = 289.24 units²
