This past week was exam week. We did packets of chapter 7-9 to prepare us for our exam. which was really hard! On friday we started learning chapter 10. In chapter 10 you dont use calculators!

formulas:
cos(alpha +/- beta)=cos alpha cos beta -/+ sin alpha sin beta
sin(alpha +/- beta)=sin alpha cos beta +/- cos alpha sin beta

In order to work these types of problems you must know your trig chart!

EXAMPLE:
Find the exact value of sin 30 degrees.
alpha would be 90 and beta would be 60.
alpha is usually the bigger number especially when subtracting.

sin(90-60)=sin 90 cos 60-cos 90 sin 60
since you are subtracting in the front you must subtract in the back.
TRIG CHART!
=(1)(1/2)-(0)(square root of 3/2)
=1and 1/2-0
sin 30 degrees=1 and 1/2.