Composition of trigonometric functions, mean value theorem

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SUMMARY

The discussion focuses on demonstrating that the function cos(cos x) is a contraction mapping using the Mean Value Theorem (MVT). The derivative of the function, |d/dx (cos(cos x))|, is expressed as |sin(cos x) sin(x)|, which is shown to be less than sin(1), confirming the contraction property. Participants seek clarification on how to establish that |sin(cos x) sin(x)| is indeed less than sin(1).

PREREQUISITES
  • Understanding of the Mean Value Theorem (MVT)
  • Knowledge of trigonometric functions and their derivatives
  • Familiarity with contraction mappings in mathematical analysis
  • Basic calculus concepts, particularly differentiation
NEXT STEPS
  • Study the Mean Value Theorem in detail, focusing on its applications in proving contraction mappings
  • Explore the properties of trigonometric functions, specifically the behavior of sin(x) and cos(x)
  • Investigate the concept of contraction mappings and their significance in fixed-point theorems
  • Learn about the implications of derivative bounds in the context of function continuity and differentiability
USEFUL FOR

Mathematics students, educators, and anyone interested in advanced calculus, particularly those studying contraction mappings and the Mean Value Theorem.

zbot1
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Homework Statement



how to show using MVT that cos(cos x) is a contraction.

Homework Equations



| d/dx (cos(cos x)) | = | sin(cos x) sin(x) | < sin 1 < 1

The Attempt at a Solution



Using that relation, the original problem is easily solved. My question is, how do we know:

| sin(cos x) sin(x) | < sin 1 ?

-zbot1
 
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zbot1 said:

Homework Statement



how to show using MVT that cos(cos x) is a contraction.

Homework Equations



| d/dx (cos(cos x)) | = | sin(cos x) sin(x) | < sin 1 < 1

The Attempt at a Solution



Using that relation, the original problem is easily solved. My question is, how do we know:

| sin(cos x) sin(x) | < sin 1 ?

-zbot1

-1<=cos(x)<=1. What does that make the range of values for sin(cos(x))?
 
Thanks!
 

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