find the area of a triangle w/ sides

Question

4x, 5x and 7x Round to the nearest hundredth

thanks for your help

Answer 1

your triangle is similar to one with sides 4,5, and 7

find the angle across from the 5 side

5^2 = 4^2 + 7^2 - 2(4)(7)cos A
cos A = .7142857
angle A = 44.415 degrees

now the area = 1/2(4x)(7x)sin A
= 14x^2(.699854)
= 9.80x^2