The Law of Cosines
The Law of Cosines – Example 2:
\(b=20, a=8, c=14\)
\(cos B= \frac {14^2+8^2-20^2}{2(14)(8)} =\frac {196+ 64 – 400}{176}=\frac{-140}{224}=-0.625\)
Since \(cosB\) is negative, \(B\) is an obtuse angle.
\(B≅128.69 ^\circ \)
Exercises for the Law of Cosines
In the ABC triangle, find the side of c.
1.
2.
3.
- \(\color{blue}{31.12}\)
- \(\color{blue}{44.68}\)
- \(\color{blue}{21.49}\)
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