The differentiable functions x and y are related by the following equation. The sine of x plus cosine of y is equal to square root of two. They also tell us that the derivative of x with respect to t is equal to five. They also ask us, find the derivative of y with respect to t when y is equal to pi over four and zero is less than x is less than pi over two. So given that they are telling us the derivative of x with respect to t and we wanna find the derivative of y with respect to t, it's a safe assumption that both x and y are functions of t. So you could even rewrite this equation right over here. You could rewrite it as sine of x, which is a function of t, plus cosine of y, which is a function of t, is equal to square root of two. Now it might confuse you a little bit.