10-1

This week was more about reviewing than learning. We had our exam on Thursday, so we only learned something new on Friday. On Friday we started Chapter 10. Section 10-1 is about finding exact values of trig functions and simplifying them. We are NOT allowed to use calculators in this section. It all comes from your trig chart and we should all know that by now since we learned it in Chapter 7.

There are two formulas you have to know in this section:
cos(alpha -/+ beta) = cos alpha cos beta -/+ sin alpha sin beta
sin(alpha +/- beta) = sin alpha cos beta +/- cos alpha sin beta

*alpha and beta come straight from your trig chart and +/- to get the angle you are looking for, no worries.

EXAMPLE 1: Find the exact value of sin30 degrees.
A). What two numbers +/- to get 30.. 90 & 60! So your alpha will be 90 and your beta will be 60.
B). Since the problem is asking for the exact value of sin, we’re going to use the second formula.
So, plug your alpha and beta into it – sin(90 degrees – 60 degrees) = sin 90 degrees * cos 60 degrees – cos 90 degrees * sin 60 degrees.
C). Now that we have our formula filled in, replace the trig functions with values from the trig chart – (1)(1/2) – (0)(square root of 3/2)
D). Your exact value is ½.

Other than finding the exact value, you will be asked to simply like the ones we did in class on Friday. All you’re doing is replacing what’s on the right with what goes on the left side. This section will come easy to you if you know your formulas and trig chart!