Question

one side of an equilateral triangle is 12cm. find its area​

Answer 1

triangle area formula- 1/2bxh
12/2=6
6x12=72

Answer 2

in a equilateral triangle, all sides are equal.
hence each slant side = 12cm
to find the height of the triangle :
use Pythagoras’ Theorem (A^2 + B^2 = C^2)
A = height
B = 6
C = 12
A^2 = 108
A = 10.392... (5s.f.)

area = ½ x base x height
= ½ x 6 x 10.392...
= 31.176
= 31.2 (3s.f.)