trigonometric eqtn

x = 2n π or 2n π + π/2

yaar mereko
x^7 +y^7 ki expansion bata de
answer mein bata donga[3]

bhai , this one is a good problem , try to think

sin^2(x) + cos^2(x) = 1
and sin^7(x) + cos^7(x) <= sin^2(x) + cos^2(x)
hence ,..the condition given to us is an extremity.
which can only be obtained when :
sinx = 0 , cosx = 1 ....or ........sinx = 1 , cosx =0
generalisation :
x = (4n+1)pie/2 or x =(2m)pie

Umm..rahul ..x=3pie/2 not satisfied.