Question

Suppose a triangle has two sides of length 42 and 35, and that the angle

between these two sides is 120°. Which equation should you solve to find the
length of the third side of the triangle?

Answer 1

you should use cosine law

it state that the third side lets name it c

c^2=a^2+b^2 -2 × a × b × cos (angle between the 2 sides)

a and b are the 2 sides given