The pentagon will be composed of 5 congruent isosceles triangles
Their equal sides = 12 and the included angle between these sides = 72°
The area of one of these = (1/2) (12^2) sin (72°) = 72sin 72°
So the area is ....5 (72)sin (72°) = 360 sin (72°) ≈ 342.38 cm^2
