Question Number 97306 by Abdulrahman last updated on 07/Jun/20
$$\mathrm{if}\:\:\:\:\:\:\:\:\:\mathrm{sin14}=\mathrm{x} \\ $$$$\mathrm{then} \\ $$$$\mathrm{cos}^{\mathrm{2}} \mathrm{22}−\mathrm{cos}^{\mathrm{2}} \mathrm{8}=? \\ $$
Commented by john santu last updated on 07/Jun/20
$$\left(\mathrm{cos}\:\mathrm{22}+\mathrm{cos}\:\mathrm{8}\right)\left(\mathrm{cos}\:\mathrm{22}−\mathrm{cos}\:\mathrm{8}\right)= \\ $$$$\left(\mathrm{2cos}\:\mathrm{15cos}\:\mathrm{7}\right)\left(−\mathrm{2sin15sin}\:\mathrm{7}\right)=\: \\ $$$$−\mathrm{sin}\:\mathrm{30}^{\mathrm{o}} ×\mathrm{sin}\:\mathrm{14}^{\mathrm{o}} \:=\:−\frac{{x}}{\mathrm{2}} \\ $$
Commented by Abdulrahman last updated on 07/Jun/20
$$\mathrm{thanks}\:\mathrm{alot} \\ $$