This week in Precalculus 11, we learned about the Sine Law. It gives us a more efficient method to solving triangles without 90° angles. However, it can only be used if an angle, its opposite side length, and one other piece of information are given.

The Sine Law is commonly written in 2 forms. The first is used when solving for a side length, and the second is used when solving for an angle.

Examples

When only given one angle using Sine Law, there could be 2 different triangles. Solve for an angle, and if it is less than 90°, find its quadrant II coterminal angle. Add this to the originally given angle, and if it is less than 180°, there are 2 possible triangles.