This week in Precalc 11 we learned sine and cosine laws in the trigonometry unit. These laws are used for triangles when there isn’t a right triangle. In this blog post I will be focusing only on the sine law.

Sine law can be used to find the side length of a triangle or an angle. Some of the basic stuff that you have to know first is that all the angles in a triangle add up to 180 degrees, so if you have two angles you would be able to find the other. Angles are labeled with capital letters and sides are lowercase letters. Another thing is that if there was an angle A the side length for that angle would be across from it, not beside.

There is one formula that you need to use, but you can change it to make it easier depending on what you need to find.

You would use this one to find the side length:

And this one to find an angle:

Now to be able to use these formulas you have to first fill in all the information that is given and figure out which variable you are solving for. Once thats figured out you only use two of the fractions that are given, one has to have the variable that you are solving for, and the other one has to have no variables.

This is how you would solve one: