Chapter 10

Chapter 10 is strictly formulas. It may not be easy to memorize all of them, but once you do this will be an extremely easy chapter. You will also need the trig chart again in this chapter! Today I'm going to explain section 10-1's formulas.

They are:

1. cos(alpha+/-beta)=cos alpha cos beta-/+sin alpha sin beta

2. sin (alpha+/-beta)=sin alpha cos beta+/-cos alpha sin beta

3. sin x+sin y=2sinx+y/2 cos x-y/2

4. sin x-sin y=2cosx+y/c sin x-y/2

5. cos x+cos y=2cosx+y/2cosx-y/2

6. cos x-cos y=-2sinx+y/2 sin x-y/2

Now for an example.(REMEMBER: in this chapter you REPLACE, NOT PLUG IN!)

Find the exact value of Sin 15
1. Since sin 15 isn't on the trig chart, you must use a formula that will make it.
2. So you will use Sin(45-30)
3. You will now get, Sin45 cos 30-cos 45 sin30
4. Using the trig chart, you get Sqrt 2/2 x sqrt 3/2 - Sqrt 2/2 x sin 1/2
5. Simplify. You get (sqrt 6-sqrt 2)/4

That's how you do thattt :)

Carleyyy :)