Originally Posted by

**Ronball** Hi I have the following I need to solve for x

.44m = Sqrt(((4*pi*6m + 2*Pi*6m) * x)^2 + (2*Pi*3.5m*x)^2)

It should be a ridiculously low number, to the third decimal place is all im looking for.

I think my problem is that im not taking the square root properly of the terms which involve x....it's been so long :S

In case anyone is wondering what this formula is for, x is the standard deviation for a measurement for both the height and the radius. .44 is the basically the cumulative standard deviation allowed for the area of a cylindrical tank. This is like grade 10 or 11 math, and I completely forget how to reduce this to solve for x :(

Alternatively if anyone wants to check my result for the partial derivatives for the surface area id appreciate it :D

Surface area of a cylinder = 2*Pi*r^2 + 2*pi*r*h

partial SA in respect to r= 4*pi*r + 2*pi*h

partial Surface area in respect to h= 2* Pi * r