Question

Suppose an isosceles triangle has two sides of length 42 and 35, and that the angle between these two sides is 120 degree. what is the length of the third side of the triangle?

a. 43.65
b.77
c.58.04
d.66.78

Answer 1

We can use the cosine rule to find the third side:
c² = a² + b² -2abcos(C)
c = √(42² + 35² - 2(42)(35)cos(120)
c = 66.78
The answer is D.