Espaces Vectoriels

Day 161 — 365 Problems for 365 Days AP Calculus limit with trig identities: lim x->0 (1 - cos x) / x^2 This is one of the most important “foundation” limits in calculus (it shows up in derivatives of sin/cos, Taylor series, and tons of contest problems). The fastest approach is to rewrite 1 - cos x using a half-angle identity, then use the classic limit sin u / u -> 1. Project Mentor helps high school students with AP self-study plans, competition prep, and research/internship guidance — see my