Question

Cos 20° cos 40° cos 60° cos 80°
where a,be N and a and b are relative prime numbers then a + b =
(A)7
(B) 19
(C) 17
(D) 33​

Answer 1

Answer:

B 19 hi yar sahi hi ki galat

Answer 2

Answer:

cos 20 cos 40 cos 80 cos 60

cos 20 cos(60-20) cos (60+20) cos 60

cos60/4 ×1/2 =1/16

16+1=17