It's the same for the substitution. It seems that for you it's common to substitute, but here, we just recognize the derivative and apply formulae of antiderivatives we know
Actually, by "here" in my previous post, I meant the equality of Chris where an antiderivative of sec*tan is sec..
Edit : thanks a bunch !
I reckon that's so. Same reason most calculators do not have them.Why ? I don't know, maybe because cot, csc, sec are known with sin, cos, tan... ~
One thing I noticed about calculators that do have them (such as the Voyage 200, TI-92, TI-89), they have the functions but only display in terms of sine and cosine. For instance, if you wanted the antiderivative of sec(x), the calculator displays it as instead of