Double Angle Formulas

Here is a list of the formulas you'll need to solve the problems:



*I recommend using this one for cosine








When solving these problems remember these three steps: PICTURE, FORMULA, ANSWER

, Quadrant IV

Find:

Now to solve for sine and cosine were going to use SOH, CAH, TOA to figure out what the sine and cosine of theta is.




*Make sure that you write the equation each time before you start to solve

plug in -4/5 for the sine of theta and 3/5 for cosine and multiply

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plug in -4/5 for your sine


solve for (-4/5) squared



subtract (32/25) from 1, think of one as (25/25) in this case.




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Now you may run into problems that seem like they have nothing to do with what we just went over, but we already know how to solve them. Here's an example...















For all the notes click HERE for a link to Mr. Corn's webpage