Click the arrows to move step by step.[br]Move the slider after each step to observe what happens.

The blue point represents any point on the sine curve :(a, sin a)[br]By drawing a tangent line at the point we can see how the gradient (m) changes at each point of the curve.[br]The red point has coordinates (a, m) showing the value of the gradient for each value of a.[br]By moving the slider, the red point will show how the gradient varies creating a new function: the derivative of the sine function.