Especially for the benefit of those students who are in trig this year, this is a quick review of what a derivative is and how we find them. Remember a derivative is nothing more than the slope of a tangent line. We can use the result as the instantaneous slope at a point. Here, we use the simple curve, y = x^2. Keep in mind that, fundamentally, we start with the normal, usual slope equation you have used for years: slope = (y2 - y1) / (x2 - x1). Check it out, and I hope it helps.