## Elementary Geometry for College Students (7th Edition)

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