#### Seed5813

##### New member

- Joined
- Jan 29, 2018

- Messages
- 24

Code:

`y=(1/8)x^2`

Code:

`y=8`

2pi Int_0^8(8x - (x^3)/8)dx

... =256pi

Dividing by 4 yields 64pi

Code:

```
64pi = 2pi Int_0^z(8x - (x^3)/8)dx
32 = Int_0^z(8x - (x^3)/8)dx
32 = 4b^2 - (b^4)/32
-(b^4)/32 + 4b^2 - 32 = 0
By quadratic formula:
b^2 = (256 + 16sqrt(12)) and 256 - 16sqrt(12)
Take three square root and multiply by 2, yielding
Diameter = 35.295 or 28.325
```