Question

prove that 2sin70°*cos20°=cos50°​

Answer 1

L.H.S.:

$= > 2 \sin(70) \times \cos(20)$

$= > 2 \cos(\pi - 70) \times \cos(20)$

$= > \cos(70 + 20) + \cos(70 - 20)$

$= > \cos(90) + \cos(50)$

$= > 0 + \cos(50)$

$= > \cos(50°) = r.h.s$

Hence, proved.