Find p,q to the expression A=p(cos8x−sin8x)+4(cos6x−2sin6x)+qsin4x does not depend upon x

Question

anonymous · Answer

COMPLICATED!
@hartnn  @mukushla  @Miracrown

anonymous · Answer

note that if it does not depend upon x so it is a constant, derivative of a constant is zero

hartnn · Answer

sorry, but how did derivative come into picture ? :P

anonymous · Answer

dunno
help me please
@hartnn

anonymous · Answer

:p I mean $A'$ must be zero, but what next, how can we find p and q in that way ?!!!?

hartnn · Answer

which means we need to select p and q such that cos and sin terms get cancelled and only a constant remains...

hartnn · Answer

maybe bringing everthing in terms of angle 4x would help

anonymous · Answer

how about those middle terms (6x)? I don't know why but it looks impossible to me :D I think there is a problem with question!!

hartnn · Answer

yeah, could be...else this is not easy enough to be asked as a homework question....its tricky...