Discovering the Law of Cosines

A triangle with sides a, b and c is drawn in the left hand panel. A regular polygon of n sides is erected on each side of the triangle. Use the blue dot in the left hand panel to adjust the ratio of b to a. Use the gold dot to vary the shape of the triangle. [You can animate the shape of the triangle by clicking on the icon in the lower left hand corner of either panel.] You can change the polygon erected on each side of the triangle by using the polygon slider.