Question

39 sin 156гр / sin 78гр умн. sin 12гр

Answer 1

$\displaystyle \frac{39\sin156а}{\sin78а\sin12а} = \frac{39\sin(180а-24а)}{\sin(90а-12а)\sin12а} = \frac{39\sin24а}{\cos12а\sin12а} =\\ \\ \\ = \frac{2\cdot39\sin24а}{2\sin12а\cos12а}= \frac{78\sin24а}{\sin24а} =78$