Week 17 – Math 11

This week in math 11 we learned about sin law. Sin law can be used to find missing sides or missing angles, and there are two different formulas to remember. the first one is for finding a missing side and that is It’s important to remember that a capital letter means its an angle and a lover case letter is a side. The second formula is the flipped version, . Aways draw a picture to help see exactly what going on and label all sides and angles, and remember that in order to use sin law you need 3 hints and two of them need to be a angle with the corresponding side.

Heres how you you use this law if you were given triangle GHJ where GH=9cm, GJ=7cm and angle H=50º and you are being asked to find angle J. First off if a picture is not given too you are going to want to draw one. Next you are going to want to know what exactly you are looking for (highlight it, star it), then you are going to want to write out the sin law you will be using and fill out the information you already have. Since you are looking for an angle you would use the second formula, once its filled in it should look like this .The first part has everything missing so it’s no help so you will want to focus on the second and third part since there is only not thing missing. You are next going to want to re arrange the equation to get J by itself. Once that is compete you should have an equation that looks like where the is being multiplied by the entire fraction. From there you would then put this into your calculator giving you 80º=J. The only other thing you need to think about is what quadrant this triangle is in, and this one would end up in quadrant II, making the angle 100º.

That is how you use the sin law to find an angle of a triangle, remember that once you have two angles you actually have all three because every triangle adds up to 180º to you would just need to subtract the two other angles from the 180 to have all three angles. You will still need to use the sin law to find a missing side though.