Question

-6sin142/sin71 * sin19

Answer 1

$frac{-6sin142}{sin71cdot sin19}=frac{-6sin142}{sin71cdot sin(90-71)}=frac{-6sin142}{sin71cdot cos71}=frac{-6sin142}{frac{1}{2}sin142}=-12\\Formyla:; ; ; 2sin alpha cdot cos alpha =sin2 alpha$