Derivative of the sine function

Click the arrows to move step by step. Move the slider after each step to observe what happens.
The blue point represents any point on the sine curve :(a, sin a) By drawing a tangent line at the point we can see how the gradient (m) changes at each point of the curve. The red point has coordinates (a, m) showing the value of the gradient for each value of a. By moving the slider, the red point will show how the gradient varies creating a new function: the derivative of the sine function.