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#1

$Old$ May 17th, 2009, 02:17 PM

Tesphen $Tesphen is offline$

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$Default$ tan and cos help!

I need a little help solving the following problem.

You are given that tanΘ = 1/2and that angle Θ is acute. Show, without using a calculator, that cos^2Θ = 5/4.

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$Old$ May 17th, 2009, 02:25 PM

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Originally Posted by Tesphen $View Post$

You are given that tanΘ = 1/2and that angle Θ is acute. Show, without using a calculator, that cos^2Θ = 5/4.

BTW it sould be $\color{blue}\frac{4}{5}$
$\tan (\phi ) = \frac{1}{2}\, \Rightarrow \,\sin (\phi ) = \frac{1}{{\sqrt 5 }}\;\& \,\cos (\phi ) = \frac{2}{{\sqrt 5 }}$ .
Can you continue?

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#3

$Old$ May 17th, 2009, 02:29 PM

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lol

ooppps, I meant ${\left(\frac{2}{\sqrt{5}}\right)}^2$

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$Old$ May 17th, 2009, 02:47 PM

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Thanks guys! That was great!

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