Ah, I see - I didn't check his formula, just noticed the answers didn't look right. Thank you for the help, that makes sense. "David
Biddulph" wrote: > I think that Rik may have intended his formula to be > =SIN(A2*PI()/10)*(A2-A1) > > If you use an interval of 1, as Rik did, the terms of the above formula sum > to 6.313752 > If you change the interval to 0.1, the sum ...