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    I have to differentiate:

    cos(½π-5x)

    My answer comes out to be:

    -5sin(½π-5x)

    Answer in the back of the book is:

    5cos5x - which one is right?

    :confused:
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    (Original post by entiti)
    I have to differentiate:

    cos(½π-5x)

    My answer comes out to be:

    -5sin(½π-5x)

    Answer in the back of the book is:

    5cos5x - which one is right?

    :confused:
    Back of the book. Yours would be right if you'd included another minus.

    cos(90 - x) = sin x.
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    ok, thanks for your help.

    That's because ½π = 90 ( in degrees ). cos( 90 - x ) = sin x is a basic rule right? Correct me if I'm wrong. :rolleyes:
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    yes, so:

    y = cos(pi/2 - 5x)
    y = sin 5x
    dy/dx = 5cos 5x
 
 
 
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Updated: June 27, 2004
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