qqp question1: How do you find the [math]\frac{dy}{dx}[/math] of [math]\tan\left(\frac{x}{y}\right) =x+y[/math]? question2: If [math](x+y)^2 -(x-y) ^2 = x^4+y^4[/math], how does one use implicit differentiation to find [math]\frac{dy}{dx}[/math]?