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Find the exact value of cos 105 degrees. In simpliest form. 

 Nov 30, 2015
edited by Guest  Nov 30, 2015
edited by Guest  Nov 30, 2015
edited by Guest  Nov 30, 2015
edited by Guest  Nov 30, 2015

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 #1
avatar+118724 
+15

Find the exact value of cos 105 degrees. In simpliest form. 


\(cos(60+45)\\ =cos60cos45 - sin60sin45\\ =\frac{1}{2}*\frac{1}{\sqrt{2}}\;\;-\;\;\frac{\sqrt3}{2}*\frac{1}{\sqrt2}\\ =\frac{1}{2\sqrt{2}}\;\;-\;\;\frac{\sqrt3}{2\sqrt2}\\ =\frac{\sqrt2}{4}\;\;-\;\;\frac{\sqrt6}{4}\\ =\frac{\sqrt2-\sqrt6}{4}\\\)

 Nov 30, 2015
 #1
avatar+118724 
+15
Best Answer

Find the exact value of cos 105 degrees. In simpliest form. 


\(cos(60+45)\\ =cos60cos45 - sin60sin45\\ =\frac{1}{2}*\frac{1}{\sqrt{2}}\;\;-\;\;\frac{\sqrt3}{2}*\frac{1}{\sqrt2}\\ =\frac{1}{2\sqrt{2}}\;\;-\;\;\frac{\sqrt3}{2\sqrt2}\\ =\frac{\sqrt2}{4}\;\;-\;\;\frac{\sqrt6}{4}\\ =\frac{\sqrt2-\sqrt6}{4}\\\)

Melody Nov 30, 2015

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