How to find the area of a triangle without the height?

Question

If the three sides are 2.5, 3, and 5, what is the area?

Answer 1

Use Heron's formula:

A = sqrt ( s (s-a) (s-b) (s-c) ),

where a, b and c are the sides and s = (a + b + c)/2

s = ( 2.5 + 3 + 5 ) / 2

s = 5.25

A = sqrt (5.25 * (5.25 - 2.5) * (5.25 - 3) * (5.25 - 5) )

A = 2.85 square units