10-3 Double Angle and Half Angle Formulas

This week I am going to explain how to work problems using double and half angle formulas. There are ALOT of formulas for this so you better be ready. Okay, so now I am going to list all the formulas for you.

Double Angle Formulas:

Half Anlge Formulas:

So now that you have all the formulas, I am going to work a few examples for you.

Example 1: 2 cos^2 10 degrees - 1

• All you would do for this problem is replace it with the formula it equals from above.
• Your answer would be cos 20 degrees.

Example 2: cos^2 4A - sin^2 4A

• All you have to do is again replace with a formula.
• Your answer would be cos 8A.

Example 3: 2 tan 25 degrees / 1-tan^2 25 degrees

• Once you would replace, you would get tan 50 degrees.

Well, I hope you understand how to work problems using double and half angles now. Glad I could help. Now I have to go work this chapter test that I have no clue how to do. GOOD BYE.

--Halie!