Finding angle X when given an inequation and a weird equation

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SUMMARY

The discussion focuses on solving the equation sin(x) + sin(2x) + sin(3x) = 0 within the interval π/2 < x < π. Participants suggest using the double-angle formula to expand sin(2x) and the sum-to-product identities for sin functions. The key steps involve rewriting sin(3x) as sin(2x + x), collecting like terms, and applying the Pythagorean identity sin²(x) + cos²(x) = 1 to facilitate factoring. This method leads to a clearer path for finding the angle X.

PREREQUISITES
  • Understanding of trigonometric identities, specifically the double-angle and sum-to-product formulas.
  • Familiarity with the Pythagorean identity sin²(x) + cos²(x) = 1.
  • Basic knowledge of solving trigonometric equations within specified intervals.
  • Ability to manipulate algebraic expressions involving trigonometric functions.
NEXT STEPS
  • Study the double-angle formulas for sine and cosine functions.
  • Learn about sum-to-product identities for trigonometric functions.
  • Practice solving trigonometric equations within defined intervals.
  • Explore advanced factoring techniques in trigonometric expressions.
USEFUL FOR

Students studying trigonometry, educators teaching trigonometric identities, and anyone looking to enhance their problem-solving skills in trigonometric equations.

Paulo Serrano
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Homework Statement



sin (x) + sin (2x) + sin (3x) = 0
http://www4b.wolframalpha.com/Calculate/MSP/MSP531196eg6ff0edb8i9400000gb08c7ag3hfbfeh?MSPStoreType=image/gif&s=8

Sorry for not following the recommended layout, it's just that this question boggles me and I don't know any relevant formulas or where to start.

I know the http://www28.wolframalpha.com/input/?i=sin+x+++sin+2x+++sin+3x+=+0,+pi/2+<+x+<+pi"but I don't know how to get to it.

Thanks in advance to whoever tries to help
 
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Do you know a formula for sinP+sinQ? (or the sum to product formula for sin?)
 
Use the double-angle formula to expand the [tex]sin(2x)[/tex] and [tex]sin(3x)[/tex] - notice that [tex]sin(3x)=sin(2x+x)[/tex] , then collect like terms and factor as much as possible while using [tex]sin^2(x)+cos^2(x)=1[/tex] to aid you in the factoring process.
 

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