How do I find the exact value without any decimals?

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- Dec 9th 2012, 10:42 AMEraser147Find the exact value of Cos 11.25 degrees
How do I find the exact value without any decimals?

- Dec 9th 2012, 10:50 AMPlatoRe: Find the exact value of Cos 11.25 degrees
- Dec 9th 2012, 10:53 AMrichard1234Re: Find the exact value of Cos 11.25 degrees
11.25 degrees = pi/16

$\displaystyle \cos 2\theta = 2 \cos^2 \theta - 1 \Rightarrow \cos \theta = \sqrt{\frac{1 + \cos 2\theta}{2}}$ (in the domain that we're interested in)

Then just apply this half-angle formula a couple times to get your answer. - Dec 9th 2012, 11:18 AMEraser147Re: Find the exact value of Cos 11.25 degrees
So it would be Sqrt 1 + (2)11.25 divided by 2?

- Dec 9th 2012, 11:27 AMskeeterRe: Find the exact value of Cos 11.25 degrees
- Dec 9th 2012, 11:40 AMEraser147Re: Find the exact value of Cos 11.25 degrees
^ Makes a lot more sense. Thanks.