Answers

2015-07-05T18:10:29+05:30
C Cos^{2}C = 1-  Sin^{2}C \\ CosC = \sqrt{1- Sin^{2}C }    \\ Cos0 =  \sqrt{1-sin^{2}0 }  \\ Cos0 =  \sqrt{1-0} =  \sqrt{1} =1

2nd method see in the attachment
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