Review of 10-3

Okay, so this week I am going to review problems in section 10-3. This is section is on how to solve problems using different formulas. These problems are very easy as long as you remember the formulas. So now I am going to list them for you.

Formulas:

• sin 2a= (2 sin a) (cos a)
• cos 2a= (cos^2 a) – (sin^2 a)
• cos 2a= 1- 2 sin^2 a
• cos 2a= 2 cos^2 a -1
• tan 2a= ( 2 tan a) / ( 1- tan^2 a)
• sin a/2= +/- sq. root of ((1 – cos a) / (2))
• cos a/2= +/- sq. root of (( 1+ cos a) / (2))
• tan a/2= +/- sq. root of (( 1- cos a) / ( 1+cos a))
• tan a/2= +/- (( sin a) / ( 1+ cos a))
• tan a/2= +/- (( 1- cos a) / (sin a))

Those are the formulas you are going to need to know for this section. So now that you know the formulas, I am going to work a few examples for you to better understand these problems.

Example: Simplify cos^2 15 degrees - sin^2 15 degrees

• cos 2(15 degrees)
• cos 30 degrees
• square root of 3 / 2 is your answer.

So that is how you work these types of problems. Hoped this helped you to remember! Byeee.

--Halie!