DE question

**neven87** · June 6th 2007, 12:29 PM

im doing my DE HW and i dont understand how the book came out with an answer.. This is separable variables with an initial value.

(dx/dt) = 4(x^2+1) the intial value is: x((pi)/4)=1

the answer is: y= sin ((1/2)x^2+c)

and i have no idea where the sin came from...i know im probaly missing a rule somewhere, thanks for any help to get the jucices going!

**Jhevon** · June 6th 2007, 12:57 PM

Originally Posted by neven87

im doing my DE HW and i dont understand how the book came out with an answer.. This is separable variables with an initial value.

(dx/dt) = 4(x^2+1) the intial value is: x((pi)/4)=1

the answer is: y= sin ((1/2)x^2+c)

and i have no idea where the sin came from...i know im probaly missing a rule somewhere, thanks for any help to get the jucices going!

be sure you don't have a typo here, or that you are looking at the right question. because as the question is stated, your answer should be of the form x = f(t) not y = f(x)

the answer i got is $x = \tan \left( 4t - \frac {3 \pi}{4} \right)$