Question

(4 Points)

Here is a triangle
Angle PQR= 120°
PQ= 6 CM
QR= 9 CM Work out the length PR​

Answer 1

Explanation:

You know the lengths of two sides and the angle between them. Use the Law of Cosines to solve the triangle.

PR^2 = 6^2 + 9^2 - 2*6*9*cos(120°)

= 36 + 81 - 108(-0.5)

= 13