Factoring, Rationalizing and Squeezing Limits — Cheat sheet

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Core rule

Use equality on nearby non-target points for factoring or rationalization. If g≤f≤hg\le f\le h nearby and g,h→Lg,h\to L, then f→Lf\to L.

lim⁡x→0sin⁡xx=1,\lim_{x\to0}\frac{\sin x}{x}=1, lim⁡x→01−cos⁡xx2=12.\lim_{x\to0}\frac{1-\cos x}{x^2}=\frac12.

Watch for

Angles must be in radians. Bounds must hold throughout a neighborhood. 0/00/0 is a prompt for analysis, not an answer.