The base of a regular pyramid is a square whose sides have a length 8 cm. If a lateral edge of this pyramid has length 20 cm, what is the surface area of the pyramid?

Answer 1

Look at one of the triangles, which is isosceles with a base of 8 and each of the equal sides of length 20

Height of triangle: let it be h
h^2 + 4^2 = 20^2
h^2 = 384
h = √384

Area of one triangle = (1/2)(8)(√384) = 4√384
Assuming the surface area consists only of the 4 triangles,
surface area = 4(4√384) or 16(8√6) = 128√6

Answer 2

Thanks, but I need the base too - that I can do by myself!

Answer 3

One edge of a right square pyramid is 6cm long. If the length of the lateral edge is 8cm, then find: its total surface area