Kim Baxter

Posted on Saturday, 01 March, 2003 - 11:28 am:

Hi... I have a calculus question in which I have to use a trigonometric substitution

ò x²
____
Ö9-x²

dx

I have substituted u=3sinq which has given me 9/2(x-x/3cosq)

could someone tell me if I am on the right track or if it is right

Ian Short

Posted on Saturday, 01 March, 2003 - 01:10 pm:

Setting x=3sinq gives dx=3cosqdq. So

òx²/ ____
Ö9-x²

dx

=ò(sin²q)(3cosq)/
Ö

9-9sin²q

dq

=ò(9sin²q)(3cosq)/3cosqdq

=ò9sin²qdq.

Is that clear?