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Question Number 192270 by universe last updated on 13/May/23

$$provethat$$$$\sin 50°+\sin 10°=\cos 20°$$

Answered by Frix last updated on 13/May/23

$$\sin (60°-10°)+\sin 10°=$$$$=\sin 60°\cos 10°-\cos 60°\sin 10°+\sin 10°=$$$$=\frac{\sqrt{3}\cos 10°}{2}+\frac{\sin 10°}{2}=\sin (10°+60°)=$$$$=\sin 70°=\cos 20°$$

Answered by mehdee42 last updated on 13/May/23

$$2sin\left(\frac{50+10}{2}\right)cos\left(\frac{50-10}{2}\right)=2sin30cos20=cos20$$

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