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Math Help - Given that:

  1. #1
    Newbie Sanjana Das's Avatar
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    Question Given that:

    (1+cosA)(1+cosB)(1+cosY)=(1-cosA)(1-cosB)(1-cosY)<br />

    Show tht one of the values of each member of this equality is sinA sinB sinY.

    plss explain with all the steps as i m in 10th std.....
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  2. #2
    MHF Contributor
    Grandad's Avatar
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    Hello Sanjana Das
    Quote Originally Posted by Sanjana Das View Post
    (1+cosA)(1+cosB)(1+cosY)=(1-cosA)(1-cosB)(1-cosY)<br />

    Show tht one of the values of each member of this equality is sinA sinB sinY.

    plss explain with all the steps as i m in 10th std.....
    Multiply both sides by (1+\cos A)(1+\cos B)(1+\cos Y), noting that, on the RHS, (1-\cos A)(1+\cos A) = (1-\cos^2A), ... etc:

    (1+\cos A)^2(1+\cos B)^2(1+\cos Y)^2=(1-\cos^2A)(1-\cos^2B)(1-\cos^2Y)

    Can you complete it now? (Hint: 1-\cos^2A=\sin^2A)

    Grandad
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  3. #3
    Newbie Sanjana Das's Avatar
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    Quote Originally Posted by Grandad View Post
    Hello Sanjana DasMultiply both sides by (1+\cos A)(1+\cos B)(1+\cos Y), noting that, on the RHS, (1-\cos A)(1+\cos A) = (1-\cos^2A), ... etc:

    (1+\cos A)^2(1+\cos B)^2(1+\cos Y)^2=(1-\cos^2A)(1-\cos^2B)(1-\cos^2Y)

    Can you complete it now? (Hint: 1-\cos^2A=\sin^2A)

    Grandad

    ya thxxxxxx
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