Constants such as Cmo which are independent of incidence disappear when the equation is differentiated with respect to alpha. It's not a trick or anything, it's just that some engineering equations couldn't be solved at all unless you set them up in an elegant way. Choosing a subtle point about which to take moments, which has the effect of putting a number of nasty terms to zero later on, is part of the art.
...kinnel...wossat mean mate....................?
I shall now leave the thread because it's becoming silly, but before I go -
ZERO LIFT!
