Answer:
51 cm^2
Explanation:
the formula for area of an icoselese triangle is
A = b * h / 2
h is a line from the angle where the 5 and 5 intersect to the middle of the third line
You can find h using the pythagoran theorm with the 5 being the hypotenuse and the a being half the third line
4^2 + b^2 = 5^2
16 + b^2 = 25
b = 3, so h = 3, so now
A = 8 * 3 / 2
A = 24 / 2
A = 12 cm^2
now we have the triangle, just multiply that by 2 (top and bottom)
12 * 2 = 24
sides
8 * 1.5 = 12
5 * 1.5 * 2 = 15
now add all of it
15 + 12 + 24 = 51