Question Number 143641 by mathlove last updated on 16/Jun/21
$$\mathrm{sin}\:\mathrm{160}−\mathrm{sin}\:\mathrm{20}=? \\ $$
Answered by Rasheed.Sindhi last updated on 16/Jun/21
$$\mathrm{sin}\:\mathrm{160}−\mathrm{sin}\:\mathrm{20} \\ $$$$=\mathrm{sin}\left(\mathrm{180}−\mathrm{20}\right)−\mathrm{sin}\:\mathrm{20} \\ $$$$=\mathrm{sin180cos20}−\mathrm{cos180sin20}−\mathrm{sin20} \\ $$$$=\mathrm{0}.\mathrm{cos20}−\left(−\mathrm{1}\right)\mathrm{sin20}−\mathrm{sin20}\:\:\:\:\: \\ $$$$=\mathrm{sin20}−\mathrm{sin20}=\mathrm{0}\:\:\:\:\: \\ $$