How to Find Maximum and Minimum Values of Sin^4theta + Cos^4theta

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SUMMARY

The discussion focuses on proving the identity sin4θ + cos4θ = 1/4 (3 + cos 4θ) and finding its maximum and minimum values. Participants suggest starting from the right-hand side (RHS) and manipulating the expression to facilitate the proof. A key insight involves rearranging terms to factor the expression effectively, leading to a clearer path toward the solution. The collaborative nature of the discussion highlights the importance of peer assistance in tackling complex mathematical proofs.

PREREQUISITES
  • Understanding of trigonometric identities
  • Familiarity with polynomial manipulation
  • Knowledge of factoring techniques
  • Basic calculus concepts for finding extrema
NEXT STEPS
  • Study trigonometric identities and their proofs
  • Learn about polynomial factoring methods
  • Explore calculus techniques for finding maximum and minimum values
  • Investigate the properties of sin4θ and cos4θ functions
USEFUL FOR

Students studying trigonometry, mathematics enthusiasts, and educators looking to enhance their understanding of trigonometric identities and polynomial expressions.

hibernator
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Homework Statement



prove that sin^4theta + cos^4 theta =1/4 (3+cos4theta).hence,find the greatest and least value of sin^4theta + cos^4 theta.

please give hints to start . no idea at all...i start from the RHS and get 2cos^4 theta - 2 cos^2 theta +1 , then how sin^4theta + cos^4 theta



Homework Equations





The Attempt at a Solution

 
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hibernator said:

Homework Statement



prove that sin^4theta + cos^4 theta =1/4 (3+cos4theta).hence,find the greatest and least value of sin^4theta + cos^4 theta.

please give hints to start . no idea at all...i start from the RHS and get 2cos^4 theta - 2 cos^2 theta +1 , then how sin^4theta + cos^4 theta

So you started at the RHS and got to this:
2cos4 θ - 2cos2 θ + 1.
You're really close, then. Split the 2cos4 θ and rearrange the terms like so:
cos4 θ + 1 - 2cos2 θ + cos4 θ
Factor the part in bold.
 
Last edited:
Amazing idea that i never thought before ! TQ so much eumyang..
 

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