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Math Help - Find the Value of the Number C

  1. #1
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    Find the Value of the Number C

    Find the value of the number C:

    (1/2)[cos^2(x)] + C = (1/4)[cos2(x)]
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  2. #2
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    Quote Originally Posted by magentarita View Post
    Find the value of the number C:

    (1/2)[cos^2(x)] + C = (1/4)[cos2(x)]
    Since it's an identity, it's true for all values of x. So substitute a simple value like x = 0. Then solve for C .....
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  3. #3
    Senior Member nikhil's Avatar
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    Quote Originally Posted by magentarita View Post
    Find the value of the number C:

    (1/2)[cos^2(x)] + C = (1/4)[cos2(x)]
    Cos2x=2(cosx)^2-1 therfor
    (cosx)^2=(1+cos2x)/2
    as
    (1/2)[cos^2(x)] +C=(1/4)[cos2(x)]
    1/2((1+cos2x)/2)+C=(1/4)[cos2(x)]
    1/4+(cos2x)/4+C=(1/4)[cos2(x)]
    1/4+C=0
    C=-1/4
    Last edited by nikhil; August 29th 2008 at 03:44 AM.
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  4. #4
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    Quote Originally Posted by nikhil View Post
    Cos2x=2(cosx)^2-1 therfor
    (cosx)^2=(1+cos2x)/2
    as
    (1/2)[cos^2(x)] +C=(1/4)[cos2(x)]
    1/2((1+cos2x)/2)+C=(1/4)[cos2(x)]
    1/2+(cos2x)/4+C=(1/4)[cos2(x)] Mr F says: That red 2 should be a 4.
    1/2+C=0
    C=-1/2
    Actually C = -1/4.

    You should have tested it using a simple value of x lol!!
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  5. #5
    Senior Member nikhil's Avatar
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    Ooooopppss

    My bad
    warning:giving solutions using gprs phone is hazardous to ur(actually mine) calculations.
    Last edited by nikhil; August 29th 2008 at 03:49 AM. Reason: Addition
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  6. #6
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    Great...

    I thank both of you very much.
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