If we want to solve for the derivative of y with respect to x, we just multiply both sides times the cosine of y squared. We get the derivative of y with respect to x is equal to cosine of y squared. Like we've seen in previous videos, this isn't that satisfying. I've written the derivative of y with respect to x as a function of y. What we're really interested in is writing it as a function of x. To do that, we need to express this somehow in terms of the tangent of y. The reason why the tangent of y is interesting is because we already know that tangent of y is equal to x.