Integrating (sin(x))^6: A Quick Solution

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SUMMARY

The integral of (sin(x))^6 can be solved using trigonometric identities and integration techniques. The solution involves rewriting sin^6(x) as (1/8)(1 - 3cos(2x) + 3cos^2(2x) + cos^3(2x)). The integration of the resulting terms can be approached by integrating 1 - 3cos(2x) directly, while cos^3(2x) requires substitution with u = sin(2x), and cos^2(2x) can be simplified using the identity cos^2(2x) = (1/2)(1 + cos(4x)).

PREREQUISITES
  • Understanding of trigonometric identities, specifically cos(2x) and sin^2(x)
  • Familiarity with integration techniques, including integration by parts
  • Knowledge of substitution methods in integration
  • Ability to manipulate polynomial expressions in trigonometric integrals
NEXT STEPS
  • Study advanced integration techniques, focusing on integration by parts
  • Learn about trigonometric substitutions in integrals
  • Explore integral tables for common trigonometric integrals
  • Practice solving integrals involving higher powers of sine and cosine functions
USEFUL FOR

Students studying calculus, particularly those focusing on integral calculus, as well as educators seeking to enhance their teaching methods for trigonometric integrals.

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Homework Statement



I just can't crack the integral of (sin(x))^6 for some reason.

What is the exact solution to this? This is not really a homework question, as an immediate reference to an integral table would be sufficient. But I just need it right away. Thanks.



Homework Equations



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The Attempt at a Solution



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Use integration by parts repeatedly.
 
Or use trig identities. [itex]cos(2x)= cos^2(x)- sin^2(x)= 1- 2sin^2(x)[/itex] so [itex]sin^2(x)= (1/2)(1- cos(2x))[/itex]. Then [itex]sin^6(x)= (sin^2(x))^3= (1/2)^3(1- cos(2x))^3[/itex][itex]= (1/8)(1- 3cos(2x)[/itex][itex]+ 3cos^2(2x)+ cos^3(2x))[/itex].

The integral of 1- 3cos(2x) is straightforward. The integral of [itex]cos^3(2x)[/itex] can be done by writing it as [itex]cos^3(2x)= cos(2x)(1- sin^2(2x))[/itex] and using the substitution u= sin(2x). The integral of [itex]cos^2(2x)[/itex] can be done by using the trig identity [itex]cos^2(2x)= (1/2)(1+ cos(4x))[/itex].
 

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