# [SOLVED]Find volume when curve rotated about y-axis

#### DeusAbscondus

##### Active member
Hi folks, could someone please take a look at this for me:

Here are the givens:

$$\text{ Find the volume when this curve is rotated about the y-axis }$$
$$y=-4lnx\ \text{ where } 0\le y \le 2$$

I have set my working out in a geogebra file, taken a screenshot and attached same below.

Would someone kindly take a look at my calculations and point out where I am going astray?

Deus Abs

#### tkhunny

##### Well-known member
MHB Math Helper
$$e^{0}\ne 0$$

Good work otherwise.

Last edited:

#### DeusAbscondus

##### Active member
$$e^{0}\ne 0$$

Good work otherwise.
Thank you kindly!

so: $$-2.2114547+2\pi \approx 3.97$$

Which is the solution given!

Do you know I kept making that error over and over again, through a frustrating hour or so; this makes me *sure* that I must find a different approach (different mind-set/attitude, perhaps) my checking procedure: cultivate an attitude of radical skepticism: something like: "question *everything* again regarding your working assumptions!"

Regs,
D'Abs

#### tkhunny

##### Well-known member
MHB Math Helper
Contrary to the too broad definition of privacy, another pair of eyes often is quite beneficial.