Period of sin4(x) + cos4(x): Find the Answer Here

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Discussion Overview

The discussion revolves around finding the period of the function sin4(x) + cos4(x). Participants explore different methods to determine the period, including algebraic manipulation and the use of individual function periods.

Discussion Character

  • Mathematical reasoning, Technical explanation, Debate/contested

Main Points Raised

  • One participant notes that the individual periods of sin4(x) and cos4(x) are both π but struggles to find the period of their sum.
  • Another participant provides a transformation of the function, showing that sin4(x) + cos4(x) can be expressed as 2 - (1/2)sin2(2x), suggesting a period of π/2.
  • A subsequent post reiterates the transformation and claims that the period is π/2, questioning why the least common multiple (LCM) of the individual periods does not yield this result.
  • Some participants discuss the reasoning behind using the LCM of the periods, with one suggesting that it gives a multiple of the period rather than the fundamental period.
  • Another participant proposes using Euler's formula as an alternative method to find the period, also concluding that it is π/2.

Areas of Agreement / Disagreement

There is no consensus on the method for finding the period, as participants present differing views on the use of LCM and the transformations applied. The discussion remains unresolved regarding the best approach to determine the period of the function.

Contextual Notes

Participants express uncertainty about the validity of using the LCM of the periods of the individual functions and how it relates to the period of their sum. There are also unresolved mathematical steps in the transformations presented.

phymatter
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i have to find the period of sin4(x) + cos4(x)

i know that the period of both the functions individually is pi , but i am unable to find the period of sum of these two functions..

pl. help!
 
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sin4(x) + cos4(x)=(sin2x+cos2x)2-2sin2x cos2x=2-1\2 sin2(2x).
 
losiu99 said:
sin4(x) + cos4(x)=(sin2x+cos2x)2-2sin2x cos2x=2-1\2 sin2(2x).

by this we get the period as pi/2 , and that's correct ,
but why can't we get this answer by finding the lcm of the period of two functions?
by that we get ans as pi!
 
Why should that give the period?
 
phymatter said:
finding the lcm of the period of two functions

This gives a multiple of the period.
 
One way to find the period is by re-expressing the function with Euler's formula and then simplify and re-express it back into a trigonometric function.

Period of the function is pi/2
 
Last edited:

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