As i pretty much say in every blog Advanced Math is getting harder and harder. Everything you learn is accumulative and has to be remembered in order to solve other problems. Right now we are still in Chapter 9 working on triangles, which trigonometry is.

9-3 is all about the Law of Sines. The law of sine is only used with NON-RIGHT TRIANGLES. You are only about to use the law of sines when you have an angle and an opposite leg value that you know.

Formula: sin (angle) = sin (angle 2)
______________ _________________
opp leg opp leg 2

TIP: you must always cross multiply to solve.

Example: A civil engineer wants to determine the distances from points A to B to a inacessible point C. From direct measurement the engineer knows the AB=25cm AngleA=110° AngleB=20°. Find AC&BC

1.You draw out your triangle from what you already know. Once draw you see the you do not know legs a or b and AngleC.
2. To find angle c subtract the two angles known by 180°.
180-110-25=50°
3.Plug into formula..
sin50/25=sin110/AC
4.Cross multiply to get BCsin50=25sin10
5.Get BC by itself by dividing 50.
6. Answer for angle BC is 25sin110/sin50 which equals 30.667
-Next solve or AC-
1.ACsin50=25sin20
2.Divide to get AC alone.
3.Answer is 25sin20/sin50 which equals 11.162

Each problem is different but you always follow the same rules. Sometimes you may have to find angles, and don't forget when solving for an angle you do the inverse.