e. f: R→ [-1, 1], f(x) = cos x f. f: R→R, f(x) = |x|. g. 9: S¹ x I→ R², g(x, y) = x. (Here, it is understood that x E S¹ and ye I.) h. h: S¹→ R², h(x, y) = (x, y). Pro

Advanced Engineering Mathematics
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ISBN:9780470458365
Author:Erwin Kreyszig
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Chapter2: Second-order Linear Odes
Section: Chapter Questions
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E,f,h,g
e.
01 (s.))
0= x 1 (010)
= (x)}
S=T=R,
f(x) = x² - 1.
ЕЯ+Я:
Problem 7. For each function, give an explicit expression for its image, and
say whether the function is an injection, surjection, or bijection. If the function
is a bijection, also give its inverse.
a. f: RR, f(x) = x³
b. f: R→ R2, f(x) = (x,x³) [here, just use the bracket notation to express
im(f).]
c. f: R→R, f(x) = x²
d. f: R→ [0, ∞), f(x) = x²
e. f: R→ [-1, 1], f(x) = cos x
f. f: R→R, f(x) = |x|.
g. 9: S¹ x I→ R2, g(x, y) = x. (Here, it is understood that x E S¹ and
ye I.)
h. h: S¹→ R², h(x, y) = (x, y).
Problem o
Transcribed Image Text:e. 01 (s.)) 0= x 1 (010) = (x)} S=T=R, f(x) = x² - 1. ЕЯ+Я: Problem 7. For each function, give an explicit expression for its image, and say whether the function is an injection, surjection, or bijection. If the function is a bijection, also give its inverse. a. f: RR, f(x) = x³ b. f: R→ R2, f(x) = (x,x³) [here, just use the bracket notation to express im(f).] c. f: R→R, f(x) = x² d. f: R→ [0, ∞), f(x) = x² e. f: R→ [-1, 1], f(x) = cos x f. f: R→R, f(x) = |x|. g. 9: S¹ x I→ R2, g(x, y) = x. (Here, it is understood that x E S¹ and ye I.) h. h: S¹→ R², h(x, y) = (x, y). Problem o
Expert Solution
Step 1

(e) f : R → [-1, 1], f(x) = cos x

     For every x € [-1, 1], we have preimage y in R such that f(y) = cos(y) = x. 

     In fact there are many pre-images given a value x in [-1, 1], one being cos-1(x) within [0, π].

     Hence, image(f) = [-1, 1].

     f is surjective. 

     But, we see, 0 ≠ 2π, but f(0) = f(2π) = 1.

     There are many more such examples. 

     Hence, f is not injective. 

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