# Math 11 Pre-Calc, Week 17

This week in math we started a new unit which is trigonometry, this was a nice little throwback to grade 10 math but in grade 11 trig its a little different. In grade 11 trig there are way more things to learn and the simplicity of SOH CAH TOA won’t cut it for grade 11 trig. In this new trig we learn that there are more quadrants and that there are 4 quadrants and in grade 10 we were doing trig in quadrant 1 for most of the time, and we know this because Sine, Cosine and tangent were all positive in quadrant 1. another thing that we learned was Sine Law, Sine law is a way that we can use to find a certain angle or length of something, for example for a Triangle each point has a letter ABC from A to B it’s 8.6 from A to C it’s 6.1 and Angle C is 65. Now say that we are trying to find the length of B to C you would use the equation of $\frac{A}{SinA} = \frac{B}{SinB} = \frac{C}{SinC}$ this is for when you’re looking a missing side but for a missing angle its the same equation just flipped. And so what we need to do right now is to find the angle of B so it can help us find the side length of BC so you would use the equation of $\frac{SinA}{A} = \frac{SinB}{6.1} = \frac{Sin65}{8.6}$ now we would use the two fractions that are filled in the most so now the equation would be $\frac{SinB}{6.1} = \frac{Sin65}{8.6}$ and what you would do to solve this is to basically isolate the B and put everything else on one side so the equation and solve from there which would give the angle B 40 degrees and from there you would keep using the same equation to find side BC and that’s how you use Sine Law.