On this problem, we need to take the derivative of sine which is cosine and then we also need to take the derivative of that t / sqrt t + 5. We need to use the quotient rule on that. So the derivative of the top times the bottom minus the derivative of the bottom times the top all over the bottom squared. So the derivative of T is one. The derivative of sqrt t + 5 is 1 / 2 square roots of t + 5 S Next we're going to get a common denominator. So we're going to multiply that first term by two square roots of t + 5 on top and bottom sqrt t + 5 times sqrt t + 5. The square roots are going to cancel, leaving us just AT +5. So we get two times the t + 5 minus the T all over two square roots of t + 5, and that whole thing is still over t + 5 if we distribute 2T plus 10 -, t / 2. And if I have sqrt t + 5 and I'm dividing by t + 5, that's the same thing as multiplying by 1 / t + 5. So now we're multiplying sqrt t + 5 * t + 5 in the denominator. So we're going to add the exponents of 1/2 + 1. When we have 1/2 + 1, we're going to get three halves. So now if we just finish by combining our like terms in the numerator, two t - t is t + 10 / 2 times the quantity t + 5 to the three halves. That whole thing was times the cosine of t / sqrt t + 5.