Find dy/dx for y=sin(x+y)

Question

A. 0
B. (cos(x+y))/(1-cos(x+y)
C. cos(x+y)
D. 1
E. None of these

I know I'm supposed to use implicit differentiation but I'm not sure how to go about it with sin

Answer 1

y = sin(x+y)
y' = cos(x+y)(1+y')
y' = cos(x+y) + y'*cos(x+y)
y' (1-cos(x+y)) = cos(x+y)
so, (B)