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Math Help - finding trignometric derivatives

  1. #1
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    finding trignometric derivatives

    so I did some steps for this problem and got stuck halfway down, please help

    find dy/dx
    y=1+x-cos(x)
    -------------------------
    ok so I got confused with the Pythagorean trig identities and 1 - cos(x) does NOT equal sin(x)
    I guess I need help STARTING the problem
    Last edited by omgeezy; October 5th 2008 at 10:37 AM.
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  2. #2
    Member Nacho's Avatar
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    if <br />
f(x) = 1 + x - \cos x<br />
you only must aplied the sum rule, I mean

    <br />
f'(x) = \left( 1 \right)^\prime   + \left( x \right)^\prime   - \left( {\cos x} \right)^\prime   = 0 + 1 - \left( { - \sin x} \right)<br />

    If you don`t know how find the derivate of sin(x), is aplied the definition

    <br />
\mathop {\lim }\limits_{h \to 0} \frac{{\cos \left( {x + h} \right) - \cos \left( x \right)}}<br />
{h}<br />
    Last edited by Nacho; October 5th 2008 at 02:17 PM.
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