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2014 Derivatives of Inverse Functions. AP Calculus. Monotonic – always increasing or always decreasing. Inverses. Existence of an Inverse: If f(x) is one-to-one on its domain D , then f is called invertible. Further, Domain of f = Range of f -1
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2014 Derivatives of Inverse Functions AP Calculus
Monotonic – always increasing or always decreasing Inverses Existence of an Inverse: If f(x) is one-to-one on its domain D , then f is called invertible. Further, Domain of f = Range of f -1 Range of f = Domain of f -1 One-to One Functions: A function f(x) is one-to one (on its domain D) if for every x there exists only one y and for every y there exists only one x Horizontal line test.
Find the inverse Switch x and y multiply distribute Collect y factor divide
REVIEW: Inverse Functions If f(x) is a function and ( x, y) is a point on f(x) , then the inverse f -1(x) contains the point ( y, x) To find f -1(x) Reverse the x and y and resolve for y. (a,b) (b,a) Theorem: f and g are inverses iff f(g(x)) = g(f(x)) = x
Restricting the Domain: If a function is not one-to-one the domain can be restricted to portions that are one-to-one.
Restricting the Domain: If a function is not one-to-one the domain can be restricted to portions that are one-to-one. Increasing ( Decreasing Increasing (3, Has an inverse on each interval
Find the derivative of the inverse by implicit differentiation ( without solving for f -1 (x) ) Remember : f -1 (x) = f (y) ; therefore, find
f(a,b) =m (a,b) Derivative of the Inverse The SLOPES of the function and its inverse at the respective points (a,b) and (b,a) are reciprocals. (b,a) f(x) slope @ a = 3 Derivative of an Inverse Function: Given f is a differentiable one-to-one function and f -1is the inverse of f . If b belongs to the domain of f -1and f /(f(x) ≠ 0 , then f -1(b) exists and
(a,b) Derivative of the Inverse The SLOPES of the function and its inverse at the respective points (a,b) and (b,a) are reciprocals. (b,a) Derivative of an Inverse Function: If is the derivative of f, Then is the derivative of f -1(b) CAUTION: Pay attention to the plug in value!!!
(4,16) ILLUSTRATION: (16,4) Find the derivative of f -1at (16,4) a) Find the Inverse. b) Use the formula.
Find the derivative of the Inverse at the given point, (b,a). EX: (-1,6) Theorem:
Inverse Functions REMEMBER: The x in the inverse (S) is the y in the original (f) If S(x) = f -1 (x), then S / (3) = If S(x) = f -1 (x), then S / (10) = 3 is the y value 10 is the y value
Last Update • 1/8/14 • Assignment: Worksheet 91