My final

Nick

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Find all a greater than zero for which the integral from zero to infinity (xa^-x^2) converges and find it's value

Sketch the polar curve r=root theta * cos theta 0<=theta<= pi over 2
And find the area enclosed by the curve
 
Nick said:
Find all a greater than zero for which \(\displaystyle \int_{0}^{\infty}\frac{x}{a^{x^{2}}}\) converges and find it's value

\(\displaystyle \lim_{L\to \infty}\int_{0}^{L}\frac{x}{a^{x^{2}}}dx\)

Perform the integration and it becomes: \(\displaystyle \lim_{L\to \infty}\left[\frac{1}{2ln(a)}-\frac{1}{2a^{L^{2}}ln(a)}\right]\)

Now, what happens to the limit as \(\displaystyle L\to \infty\)?. What remains?. What values of 'a' is ln defined?.



Sketch the polar curve r=root theta * cos theta 0<=theta<= pi over 2
And find the area enclosed by the curve

Is that \(\displaystyle r=\sqrt{\theta cos\theta}, \;\ -\leq \theta \leq \frac{\pi}{2}\)?.
 
For all a greater than zero except one?

No it is (root theta) times cos theta
 
Nick said:
For all a greater than zero except one?

For all \(\displaystyle a>1\)

No it is (root theta) times cos theta

\(\displaystyle r=\sqrt{\theta}cos\theta\)

\(\displaystyle \frac{1}{2}\int_{0}^{\frac{\pi}{2}}\theta\cdot cos^{2}(\theta)d\theta\)
 
I didn't get why it must be greater than 1 I'd get an answer if I had half which is less than one, can you please tell me why?
And about the other question will the graph be a petal in the first quadrant or will it be a circle or what exactly?
And thanks a lot for replying..
 
Ok! We can not take the numbers less than one because when I take half for example 1 to the power infinity is not defined?
 
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