$\displaystyle

xy = sin(x^2 + y^2)

$

$\displaystyle

x \cdot y' + y = sin(x^2 + y^2)

$

when i take the derivative of the right side is it:

$\displaystyle

cos(x^2 + y^2) \cdot 2x \cdot 2yy'

$

or

$\displaystyle

cos(x^2 + y^2) \cdot 2x + cos(x^2 + y^2) \cdot 2yy'

$

or none of the above?

thanks