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Unformatted text preview: Chapter Review true/false questions on page 195 #1: “If f is onetoone, with domain R , then f –1 ( f (6)) = 6.” ..?.. Answer: True. But note that f ( f –1 (6)) need not be defined; e.g., let f ( x ) = – exp( x ) or exp( x ) + 6. #2: “If f is onetoone and differentiable, with domain R , then ( f –1 ) ′ (6) = 1/ f ′ (6).” ..?.. Answer: False. It’s equal to 1/ f ′ ( f –1 (6)) (assuming that the denominator isn’t zero), and it’s easy to cook up examples like f ( x ) = x 3 where the two quantities are unequal. #3: “The function f ( x ) = cos x , – π /2 ≤ x ≤ π /2, is oneto one.” ..?.. Answer: False (note for instance that cos π /2 = cos – π /2). But f ( x ) = cos x , 0 ≤ x ≤ π is onetoone, as is f ( x ) = sin x , – π /2 ≤ x ≤ π /2. #4: “tan –1 (–1) = 3 π /4” ..?.. Answer: False! tan(3 π /4) = –1, but since the range of tan –1 is ( π /2, π /2) we must have tan –1 (–1) = – π /4....
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This note was uploaded on 02/13/2012 for the course MATH 141 taught by Professor Staff during the Fall '11 term at UMass Lowell.
 Fall '11
 Staff
 Calculus

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