Question

Find C.Round to the nearest tenth.20 ft22 ftoA 18 ft BC = [? ]°Law of Cosines: c2 = a + b2 - 2ab cos C

Answer 1

Using Cosine rule;

`\begin{gathered} c^2=a^2+b^2-2ab\cos C \\ \text{Where;} \\ a=22,b=20,c=18,C=\text{?} \end{gathered}`

Thus, we have;

`\begin{gathered} 18^2=22^2+20^2-2(22)(20)\cos C \\ 324=484+400-880\cos C \\ \cos C=(884-324)/(880) \\ \cos C=0.6364 \\ C=\cos ^(-1)(0.6364) \\ C=50.5^o \end{gathered}`