C-09-Q149mediumsingle_mcqcos80∘\cos 80^\circcos80∘ equals—asin10∘\sin 10^\circsin10∘bcos10∘\cos 10^\circcos10∘ctan10∘\tan 10^\circtan10∘dsin80∘\sin 80^\circsin80∘ব্যাখ্যাBecause 80∘=90∘−10∘80^\circ=90^\circ-10^\circ80∘=90∘−10∘, the angles are complementary and cos80∘=sin10∘\cos 80^\circ=\sin 10^\circcos80∘=sin10∘ by the cofunction rule.