### Home > A2C > Chapter 8 > Lesson 8.2.2 > Problem 8-136

8-136.

Find the value of

*x*in each triangle. Homework Help ✎

Use the Law of Cosines.

*C*^{2} = *A*^{2} + *B*^{2} − 2*AB*cos(*c*)

(*x*)^{2} = (15)^{2} + (21)^{2} − 2(15)(21)cos(40°)

*x* ≈ 13.542

Find the last angle, then use the Law of Sines.

*x* ≈ 68.770