This right over here, this is the same thing. Let me write it this way. This is the same thing as sine of y over cosine of y whole thing squared, which is, of course, the same thing as 1 over 1 plus tangent of y squared. This is equal to this. Why is that useful? We know that x is equal to tangent of y. This is going to be equal to 1 over 1 plus tangent of y is equal to x squared, which is pretty exciting.