Question

2. Show that cos 10° cos 30° cos 50° cos 70°= 3/ 16.​

Answer 1

Answer:

cos10.cos30.cos50.cos70 = 3/16

L.H.S. = cos30.cos10.cos50.cos70

= root(3)/2 × cos10.cos50.cos70

= root(3)/4 × (cos60 + cos40)cos70

= root(3)/8 × 2cos60.cos70 + 2cos40.cos70

= root(3)/8 × (cos70 + cos110 + cos30)

= root(3)/8 × (cos70 - cos70 + root(3)/2)

= [root(3) × root(3)] / (8×2)

= 3/16 = R.H.S.

Answer 2

Answer:

your answer attached in the photo