I chose to talk about these laws because it will definitely be important for grade 12, as they allow to solve non-right triangles.

The Sine Law relates the ratios of the lengths of the sides of a triangle to the sines of its angles.

The Cosine Law relates the lengths of the sides of a triangle to the cosine of one of its angles.

Formulas:

Sine Law:

Cosine Law:

Examples:

Given A=30°, B=45°, and a=10:

Given a=7, b=10, C=60°

As you can see, use sine when you know two angles and one side or two sides and a non-included angle. Use cosine when you know two sides and the included angle or all three sides.