What is the derivative of y=tan(x+y)?

1 Answer
Jul 18, 2016

:. dy/dx=-(1+y^2)/y^2, or,

=-csc^2(x+y)

Explanation:

y=tan(x+y) rArr tan^-1y=x+y rArr tan^-1y-y=x

Diff.ing w.r.t. y, we have,

1/(1+y^2)-1=dx/dy

:. (1-1-y^2)/(1+y^2)=dx/dy

:.-y^2/(1+y^2)=dx/dy

:. dy/dx=1/(dx/dy)=-(1+y^2)/y^2, or,

dy/dx=-{1+tan^2(x+y)}/tan^2(x+y)=-sec^2(x+y)/tan^2(x+y)=-csc^2(x+y)#