math/geometry
posted by katie on .
What are the surface areas of this two figures?
a) a triangular pyramid with base of 5 cm, an altitude of the base of 8.7 cm and a slant height = 6.9 cm
b) a square pyramid with a slant height of 5.2cm and an altitude of the triangle of 9cm.

Surface area of any pyramid is base area+ 1/2 slantheight*perimeter.
a) To get base area, we use Heron's formula
Area= sqrt(s(sa)(sb)(sc))
where s is one half perimeter or
Base Area= sqrt(7.5*2.5)^3)=you do it.
Slant height= sqrt (6.9^2 + (.5*8.7)^2)
Perimeter=15
b) I don't see how the altitude can be greater than the slant height. 
got it!

I assume you caught my typo...
base area=sqrt(7.5(2.5)^3)