First, we have to find the length of each side of triangle. Equilateral triangle means 3 sides r in same length, so each side will be 21 ÷ 3 = 7 Now we need to calculate the height of the triangle. We can do this by Pythagoras theorem Let the height be h (7/2)^2 + x^2 = 7^2 The area should be 6.0621778265 Or u can say 6.06 corrected to 3 sig fig
