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Vertical asymptote (limit definition)
x = a is a vertical asymptote if lim x→a⁻ f(x) = ±∞ or lim x→a⁺ f(x) = ±∞ (at least one one-sided limit is infinite)
Horizontal asymptote (limit definition)
y = L is a horizontal asymptote if lim x→∞ f(x) = L or lim x→−∞ f(x) = L
Definition of derivative (h-form)
f′(x) = lim h→0 [f(x+h) − f(x)] / h
Definition of derivative at a point (x→a form)
f′(a) = lim x→a [f(x) − f(a)] / (x − a)
Definition of continuity at x = a
1) f(a) is defined; 2) lim x→a f(x) exists; 3) lim x→a f(x) = f(a)
Intermediate Value Theorem
If f is continuous on [a, b] and k is between f(a) and f(b), then there is at least one c in (a, b) with f(c) = k
Squeeze Theorem
If g(x) ≤ f(x) ≤ h(x) near a and lim x→a g(x) = lim x→a h(x) = L, then lim x→a f(x) = L
Types of discontinuities
Removable (hole), Jump (left and right limits exist but differ), Infinite (vertical asymptote), Oscillating (e.g. sin(1/x) at 0)
Where a function is not differentiable
Discontinuity, Corner (e.g. |x| at 0), Cusp (e.g. x^(2/3) at 0), Vertical tangent (e.g. cube root of x at 0)
Average rate of change on [a, b]
[f(b) − f(a)] / (b − a), the slope of the secant line
Special trig limit: lim x→0 sin(x)/x
1
Special trig limit: lim x→0 (1 − cos x)/x
0
Special trig limit: lim x→0 sin(kx)/x
k
Constant rule
d/dx [c] = 0
Constant multiple rule
d/dx [c·f(x)] = c·f′(x)
Power rule
d/dx [xⁿ] = n·xⁿ⁻¹
Product rule
d/dx [f·g] = f′g + fg′
Quotient rule
d/dx [f/g] = (g·f′ − f·g′) / g² (low d-high minus high d-low, over low squared)
Chain rule
d/dx [f(g(x))] = f′(g(x))·g′(x)
d/dx [sin x]
cos x
d/dx [cos x]
−sin x
d/dx [tan x]
sec²x
d/dx [cot x]
−csc²x
d/dx [sec x]
sec x tan x
d/dx [csc x]
−csc x cot x
d/dx [eˣ]
eˣ
d/dx [aˣ]
aˣ · ln a
d/dx [eᵘ] (chain rule)
eᵘ · u′
d/dx [ln x]
1/x (also true for ln|x|)
d/dx [logₐ x]
1 / (x · ln a)
d/dx [ln u] (chain rule)
u′/u
d/dx [arcsin x]
1 / √(1 − x²)
d/dx [arccos x]
−1 / √(1 − x²)
d/dx [arctan x]
1 / (1 + x²)
d/dx [arccot x]
−1 / (1 + x²)
d/dx [arcsec x]
1 / (|x| · √(x² − 1))
d/dx [arccsc x]
−1 / (|x| · √(x² − 1))
Derivative of an inverse function
(f⁻¹)′(a) = 1 / f′(f⁻¹(a)). If f(b) = a, then (f⁻¹)′(a) = 1/f′(b)