Homework Help: CALCULUS (REPOST)

Posted by Anonymous on Tuesday, May 29, 2012 at 7:40pm.

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) - MathMate, Tuesday, May 29, 2012 at 8:59pm
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) - Anonymous, Wednesday, May 30, 2012 at 8:51am
y=sin(pi^2)-3 yields approximately -3.430301217, which still doesn't fit the bill for the options I am given.
CALCULUS (REPOST) - MathMate, Wednesday, May 30, 2012 at 2:29pm
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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