Question

A triangle ABC. If a = 100 inches, b = 60 inches, and C= 60°, Find c.
Use the low of cosines

Answer 1

`\textit{Law of Cosines}\\\\ c^2 = a^2+b^2-(2ab)\cos(C)\implies c = √(a^2+b^2-(2ab)\cos(C)) \\\\[-0.35em] ~\dotfill\\\\ c = √(100^2+60^2~-~2(100)(60)\cos(60^o)) \implies c = √( 13600 - 12000 \cos(60^o) ) \\\\\\ c = \sqrt{ 13600 - 12000 \cdot (1)/(2) }\implies c=√(7600)\implies c=20√(19)\implies c\approx 87.18`