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Math Help - differentiating trig ratios

  1. #1
    Senior Member furor celtica's Avatar
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    differentiating trig ratios

    find the equation of the tangent to the curve y=cosA + 3sinA at the point where A= pi/2
    so i took A=pi/2 to get y= 2sqrt2 and m=sqrt2, with the resulting equation being y=sqrt2(A+2-(pi/2))
    apparently that is so wrong, and the answer is y+A=3+(pi/2)
    i need help here
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  2. #2
    Super Member redsoxfan325's Avatar
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    Quote Originally Posted by furor celtica View Post
    find the equation of the tangent to the curve y=cosA + 3sinA at the point where A= pi/2
    so i took A=pi/2 to get y= 2sqrt2 and m=sqrt2, with the resulting equation being y=sqrt2(A+2-(pi/2))
    apparently that is so wrong, and the answer is y+A=3+(pi/2)
    i need help here
    Derivative is -\sin A+3\cos A. Plug in \pi/2 to get m=-1. Go from there.
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  3. #3
    Senior Member furor celtica's Avatar
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    ha ha good point i had plugged in pi/4
    thanks
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