Question

вычислите sin20 cos40 +cos20 sin40

Answer 1

$sin \alpha \cdot cos \beta +cos \alpha \cdot sin \beta =sin( \alpha + \beta )\\\\sin20\, cos40+cos20\, sin40=sin60=\frac{\sqrt3}{2}$

Answer 2

$sin20cos40+cos20sin40=sin(20+40)=sin60= \frac{ \sqrt{3} }{2}$