Chapter 12.6, Problem 11WE

To determine

To find the indicated part of triangle ABC.

Answer to Problem 11WE

  $C={87.4}^{\circ }$

Explanation of Solution

Given information :

  

Here we shall use the cosine formula.

Cosine formula states that,

  $\cos A=\frac{b^2+c^2-a^2}{2bc}$

Now we have to find largest angle.

Largestangle is always opposite to the largest side.

Hence we find the angle opposite to largest side.

Hence we put the values given,

  $\begin{array}{l}\cos C=\frac{{1.6}^2+{0.9}^2-{1.8}^2}{2\left(1.6\right)\left(0.9\right)}\\ \cos C=\frac{0.13}{6.08}\\ C={\cos }^{-1}-0.02138\\ C={87.4}^{\circ }\end{array}$