Question

Find BC. law of cosine 2A. 30.7 kmB. 26.6 kmC. 31.4 kmD. 25 km

Answer 1

Solution: D. 25 KM

Analysis:

We can find BC with the law of cosine. We know two sides and the included angle.

`\begin{gathered} BC^2=AB^2+AC^2-2AB\ast AC\ast cosA \\ BC=√((14)^2+(21)^2-2\ast14\ast21\ast cos(89)) \\ BC=√(196+441-10.26) \\ BC=√(626.74)=25.03\text{ } \end{gathered}`