Write the value of

Write the value of

If sin 2A = λ sin 2B, then write the value of

If cos (A + B) sin (C – D) = cos (A – B) sin (C + D), then write the value tan A tan B tan C.

Mark the Correct alternative in the following:

cos 40^o + cos 80^o + cos 160^o + cos 240^o =