# Week 17 in Precalculus

This week in Precalc 11 we learned a new trigonometry formula known as the sine law. Sine law is used to find the angles and side length of triangles that don’t contain a ninety degree angle. To use this formula you need 3 pieces of information, 2 of which must correspond to one another. For example if you have angle C you need the side length c.

The equation you can use for sine law is:

The equation for sine law can be reciprocated depending on what you are trying to find. If you are looking for an angle, you would put the sin’s in the numerator and the side length in the denominator. Vise-versa with finding a side length.

When solving with sine law, you must choose on fraction that has a completed numerator and denominator and another fraction that has either the numerator filled out or the denominator.

Then you must isolate the variable. To do this you have to get rid of the uncompleted fractions denominator and you also must get rid of the trig function attached to the variable on the numerator. To do this you must take sin and inverse it. For example: