# The Law of Sines - Proof

- Author:
- Irina Boyadzhiev

- Topic:
- Sine

Given is an arbitrary triangle with sides , and and angles , and . Prove that
, where is the diameter of the circle through the vertices.

- Drag the orange vertices in counterclockwise direction as far as they can go.
- Use the resulting right triangles to write trigonometric ratios involving the green side, the red side
, and the green angle. - Experiment with different triangles.