That is exactly what I was looking for, thankyou very much. Now to decipher it and plug in my own data 
Ok, I've had an attempt at putting in my data and performing a fit, please see the attached. I'm not sure what I'm dong wrong to be honest, I suspect my angles are giving the issue somewhere along the line. I thought I understood the worksheet - obviously not DOH!
Anyone out there that can offer up any advice (other than give up on Math)?
Thankyou.
