Posted by Josh on .
I am trying to work out the area and perimeter of an equilateral triangle but am only given the altitude (12cm), i have tried everything from c^2 = a^2 + b^2 to b x h / 2 and nothing seems to work. How do i work this out with only one measurement?

Maths 
drwls,
Since you know it is equilateral also, the length of a side (c) must be given by c^2 = 12^2 + (c/2)^2
(3/4)c^2 = 12^2
c = 12/[(1/2)sqrt3] = 18.856
You could also write it at 12/sin60
Area = (1/2)(12)(18.856) = ?
Perimeter = 3 c = ?