Week 17 – Sine Law and Cosine Law

This week we learned how to use Sine Law and Cosine Law to find the angles and sides of triangles that aren’t right angles.

Sine and Cosine Law are used to solve for angles and sides of a triangle that isn’t a right triangle.

Sine Law is used when you’re able to use the formula \frac{a}{sin A}=\frac{b}{sin B}=\frac{c}{sin C}. In order to use the formula you must have all values of one fraction, and half of 1 other. This way, you can solve for an angle/side you’re missing. It can be any part of the formula, as long as one + half of another is given.

Cosine law is used when two sides and one angle are given to you, but you’re trying to find the missing side. The formula used is a^2=b^2+c^2-2bc(cos A) for finding a side, or cos A=\frac{b^2+c^2-a^2}{2bc}.

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