Length of Remaining Side

This question can be solved using the Law Of Cosines.

According to the law of cosines if $\theta$ is the angle between two sides (namely a and b) the other side(side c) can be found using this relation:

$c^2=a^2 + b^2 - 2ab.\cos\theta$

Using the given values and substituting them in the equation given above we can find the length of the unknown side.

Given: $a = 9,b = 13,\theta=60^\circ=\frac{1}{2}$

$c^2 = 9^2 + 13^2 - 2\times9\times13.\cos60^\circ$

$= 81 + 169 - 117\times2\times\frac{1}{2}$

$= 250 - 117$

$= 133$

$c^2 = 133$

The answer to the question is 133

use the cosine law in solving