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Math Help - cos45=sin45=1/2root2

  1. #1
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    cos45=sin45=1/2root2

    Sorry! Made a mistake in the first post... this is the correct question



    By considering a right angled isosceles triangle, or otherwise, show that

    1 + 2 sin 45
    5 cos 45 - 2 sin 45

    in the form a + b root 2 where the constants a and b are to be found...
    Last edited by mathmo; February 2nd 2009 at 08:54 AM.
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  2. #2
    MHF Contributor
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    West Malaysia
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    RE :

    Quote Originally Posted by mathmo View Post
    I dont understand this:

    By considering a right angled isosceles triangle, or otherwise, show that

    cos 45 = sin 45 = 1/2 root 2
    5 cos 45 - 2 sin 45

    in the form a + b root 2 where the constants a and b are to be found...

    PLEASE help!

    You can draw a right angle triangle with equal length of 1 and hypothenus \sqrt{2} . From there , you can show that cos{45}=sin{45}=\frac{1}{\sqrt{2}}


     5cos{45}-2sin{45}=\frac{5}{\sqrt{2}}-\frac{2}{\sqrt{2}}=\frac{3}{\sqrt{2}}<br />
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