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Learn about one-to-one functions, inverse functions, rules, notation, finding inverses, and special numbers like e in calculus.
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Math 1304 Calculus I 1.6 Inverse Functions
1.6 Inverse functions • Definition: A function f is said to be one-to-one if f(x) = f(y) implies x = y. • It never takes on the same value twice • Horizontal Line Test: A function is one-to-one if and only if no horizontal line intersects its graph more than once.
Inverse Functions • Definition: Let f and g be functions. They are said to be inverse if y = f(x) ↔ g(y) = x • Theorem: If f is a one-to-one function then it has an unique inverse. • Notation: the inverse of f is denoted by f-1
Rules for inverses • f-1(f(x)) = x, for all x in the domain of f • f(f-1 (x)) = x, for all x in the domain of f-1
Finding an inverse • Write y = f(x) and solve for x in terms of y.
Logarithms are inverse to exponentials • loga(y) = x iff y = ax
Laws for logarithms • See page 64
Natural Logarithms • Natural = base e • ln(x) = loge(x)
The number e • e = 2.718281828… is a special number that is used as a base for exponential functions in calculus