Solving a Trigonometric Equation with Identities

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SUMMARY

The discussion focuses on solving the trigonometric equation sin x + sin 3x + sin 2x = 1 + cos 2x + cos x. The key identities utilized include cos²x + sin²x = 1, cos²x - sin²x = cos 2x, and sin(a + b) = sin(a)cos(b) + sin(b)cos(a). The user successfully applied the identities sin x + sin y = 2 sin((x+y)/2) cos((x-y)/2) and cos 2x = 2 cos²(x) - 1 to derive the general solution in radians for x.

PREREQUISITES
  • Understanding of basic trigonometric identities
  • Familiarity with the sine and cosine functions
  • Knowledge of solving trigonometric equations
  • Ability to manipulate algebraic expressions involving trigonometric functions
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  • Study the derivation and applications of the sine addition formula
  • Explore advanced trigonometric identities and their proofs
  • Learn about solving higher-order trigonometric equations
  • Investigate graphical methods for solving trigonometric equations
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Students, educators, and anyone interested in mastering trigonometric equations and identities, particularly those preparing for exams or enhancing their mathematical problem-solving skills.

Johnny Leong
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How to solve: sin x + sin 3x + sin 2x = 1 + cos 2x + cos x, give general solution in radians for x.
How to get start?
Anyone could help me, please?
 
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You will need the following identities:
[tex]\cos^{2}x+\sin^{2}x=1,\cos^{2}x-\sin^{2}x=\cos2x[/tex]
[tex]\sin(a+b)=\sin(a)\cos(b)+\sin(b)\cos(a)[/tex]
 
I have solved the problem. I have used the identities:
sin x + sin y = 2 sin (x+y)/2 cos(x-y)/2 and cos 2x = 2 cos^2 (x) - 1.
With these two identities, it's easy to solve the problem.
 

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