
Estimation d'erreur: demander rayon ou ordre.
Limit with given pseudo-expansions.

Taylor exercises: 
	Deliberate faute: wrong center in o(), etc.
	Add false terms, ask for Taylor to a certain degree.
	Give Taylor, ask for second derivative on a point
		(with answer `we cannot know')

Given precision for x-x0=epsilon, ask for anticipated precision when
	x-x0=epsilon/4.

ch(x) is even because odd terms vanish near 3, pi, ...
	no because implication has no reason
	no because hypothesis is false
	no because neither the hypothesis nor implication is true.

