chapter 4.2 mean value theorem · 2020. 12. 23. · chapter 4.2 mean value theorem. 2 rolle's...
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Chapter 4.2Mean Value Theorem
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Rolle's TheoremLet f be a function. If:1. f is continuous on the closed interval [a, b];2. f is differentiable on the open interval (a, b);3. f(a) = f(b)Then ∃ a number c in (a, b) ∋ f '(c) = 0
x
y
a b
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f is differentiable on the open interval (a, b)to show this, derivative has to exist at every point on (a, b)
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Mean Value TheoremLet f be a function. If:1. f is continuous on [a, b];2. f is differentiable on (a, b);Then ∃ a number c in (a, b) ∋
f '(c) = f(b) f(a) b a
Tangent and Secant line are parallel!
connects instantaneous rate of change with average rate of change
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ex: For the function f(x) = x 2 on the interval [0, 2], show the MVT exists and then find a solution to satisfy the MVT.
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ex: For the function f(x) = x 3 x on the interval [0, 2], show the MVT exists and then find a solution to satisfy the MVT.
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ASSIGNMENTp. 202 #13
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Recall: Dig deep for precalc knowledge =)
What does f(x) = |x| look like?
What does f(x) = |x 1| look like?
What does f(x) = |x 1| + 3 look like?
**Absolute value graphs aren't differentiable at their "corner"
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ex: Explain why the MVT fails on the interval [1, 1]:a. f(x) = |x| + 1
b. f(x) = x3 + 3 for x < 1x2 + 1 for x ≥ 1
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Let f(x) = 1 x 2 on [1, 1]. Show that MVT exists and if so, find the point where the tangent line is parallel to the secant line AB.
√
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ex: Let f(x) = x on the interval [1, 1]. Does the MVT apply and if so, find the point where the tangent line is parallel to the secant AB.
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ex: For the equation f(x) = 3x x 2 on the interval [1, 3], write the equation of the tangent and secant line.
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ASSIGNMENTp. 202 #913
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Increasing/Decreasing FunctionsWith MVT, we can identify exactly where graphs rise and fall Functions with positive derivatives are
increasing (f ' > 0) Functions with negative derivatives are
decreasing (f ' < 0)
ex: The function f(x) = x 2 is:a. Decreasing on ( ∞, 0] since f '(x) = 2x < 0 on ( ∞, 0)b. Increasing on [0, ∞) since f '(x) = 2x > 0 on (0, ∞)
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ex: Find all extreme values of f(x) = x 3 4x. Then determine where the function is increasing and decreasing.
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ASSIGNMENTp. 202 #1516, 21, 22, 25