#### Answer

$\frac{sine 40°}{5.3}$ = $\frac{sine 60°}{c}$

#### Work Step by Step

Given a=5.3, α =40° β=80°
Using theorem 11.4.2
By law of sines
$\frac{sine α}{a}$ = $\frac{sine γ}{c}$
$\frac{sine 40°}{5.3}$ = $\frac{sine (180° -(α + β))}{c}$
$\frac{sine 40°}{5.3}$ = $\frac{sine (180° -(40 + 80))}{c}$
$\frac{sine 40°}{5.3}$ = $\frac{sine (180° -120)}{c}$
$\frac{sine 40°}{5.3}$ = $\frac{sine 60°}{c}$