Counter examples to disprove mappings?

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SUMMARY

This discussion focuses on counterexamples to disprove specific mathematical statements regarding real-valued functions. The participants confirm that a real-valued odd function can be strictly monotonic, using the hyperbolic sine function, sinh(x), as an example. They also explore the concept that a periodic function can be transformed through phase shifts to no longer be classified as odd or even. Additionally, they discuss that a real-valued monotonic function can indeed be even, exemplified by the constant function f(x) = 2.

PREREQUISITES
  • Understanding of real-valued functions
  • Knowledge of odd and even functions
  • Familiarity with periodic functions
  • Concept of monotonicity in functions
NEXT STEPS
  • Research the properties of hyperbolic functions, specifically sinh(x)
  • Explore phase shifts in periodic functions and their effects on symmetry
  • Study the definitions and examples of odd and even functions
  • Investigate monotonic functions and their classifications
USEFUL FOR

Mathematicians, educators, and students interested in advanced function properties, particularly those studying real-valued functions and their classifications.

xlalcciax
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give counter examples to disprove the following statements:
a) a real valued odd function cannot be strictly monotonic
b) a real valued periodic function must be odd or even
c) a real valued monotonic function cannot be even


a) sinh(x) ??
b)
c)
 
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Yes, (a) is correct!
 
micromass said:
Yes, (a) is correct!

Thanks!
Can You give me some clues for b) ?
 
Pick your favorite periodic function and transform it so that it is neither even nor odd...
 
xlalcciax said:
Thanks!
Can You give me some clues for b) ?

Think of a periodic function that is odd or even. Now phase shift it slightly. Is it still odd or even?
 
nicksauce said:
Think of a periodic function that is odd or even. Now phase shift it slightly. Is it still odd or even?


yeah. i have got it now!
what about c) ? f(x)=2 ??
 
xlalcciax said:
Thanks!
Can You give me some clues for b) ?
Any odd function which is continuous on (−∞, +∞), passes through the origin.

Take an odd periodic function & shift it up or down.
 

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