To find the slope of a tangent line, find the slope of a line passing through two points and move the points closer together. When they overlap, you’ll have your answer. But there's a trick that uses calculus and the magic of dividing by zero. Instead of finding the tangent line, it's much easier to find the slope of a line that touches the curve at two points. If you move those two points closer and closer together, you get a line that's close to the one you wanted. | Another Math

How to find the slope of the tangent line given a point | Prof D