Question

prove that cos 20cos40cos60cos80=1/16​

Answer 1

Answer:

cos 20 = 0.9397

cos 40 = 0.7660

cos 60 = 0.5000

cos 80 = 0.1736

LHS: cos 20`cos 40`cos 60`cos 80 = (0.9397 * 0.7660 * 0.5000 * 0.1736) = 0.0624795254

= 0.0625

RHS: 1/16 = 0.0625

LHS = RHS