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Math Help - derivative of sin x

  1. #1
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    derivative of sin x

    Hi,
    I just want to know if there is a difference between the derivative of sin x and sin x, where x is in radians & x is in degree.
    My textbook says the derivative of sin x is cos x, if and only if x is in RADIANS. But now I am asked to work out the derivative of sin x. I think d(sin x)/dx shouldnt equal to cos x because x is not in radians. If I am making a right point here, what is the derivative of sin x?
    Really need your help
    Thank you!
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  2. #2
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    Convert x degrees to radians and take the derivative of that?

    y' = \frac{d}{dx}\sin\frac{x\pi}{180}.

    Degrees and radians are interchangeable, so you can substitute one for another in a trig equation, so long as they come out to be the same when converted back.

    Product rule inside a quotient rule inside a chain rule.

    This is a complete shot in the dark, so I may be wrong on this.
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  3. #3
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    Got y' = 0 as my answer. Didn't even need the chain rule. When I got to that point, I just had y' = \sin(0).
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  4. #4
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    f'(x) = (π/180)cos(πx/180)

    i think..(not so confident anymore after having several posts edited by the mods :P)
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  5. #5
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    Quote Originally Posted by metlx View Post
    f'(x) = (π/180)cos(πx/180)

    i think..(not so confident anymore after having several posts edited by the mods :P)
    i got the same answer too
    thank you guys for all the help
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  6. #6
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    Ignore this post. I was an idiot and mixed up the quotient rule and product rule signs.
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