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CALCULUS (REPOST)

posted by on .

If dy/dx = x (cos x^2) and y = −3 when x = 0, when x = pi, y = .

A. −3.215
B. sqrt(2)
C. 1.647
D. 6
E. 3pi

For some odd reason, I keep getting -0.5325989. I can't come up with any of the answers given.

  • CALCULUS (REPOST) - ,

    I=∫ xcos(x²)dx
    sub u=x², du=2xdx
    I=∫cos(u)du/2
    =sin(u)/2+C
    When x=0, u=0, y=-3 => C=3
    so
    y=sin(x²)/2-3
    So calculate
    y=sin(π²)-3

    Note that if you use your calculator, make sure you put the angle to be in radians mode to get the correct answer.

  • CALCULUS (REPOST) - ,

    y=sin(pi^2)-3 yields approximately -3.430301217, which still doesn't fit the bill for the options I am given.

  • CALCULUS (REPOST) - ,

    Sorry that there was a typo (I forgot to divide sin(x²) by 2):
    y=sin(x²)/2-3
    So calculate
    y=sin(π²)/2-3

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