Why sinxcos2x = (sin3x - sinx)*0.5

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SUMMARY

The equation sin(x)cos(2x) = (sin(3x) - sin(x)) * 0.5 can be proven using trigonometric identities. Specifically, the identity for sin(3θ) = 3sin(θ) - 4sin³(θ) and cos(2θ) = 1 - 2sin²(θ) are essential for simplifying both sides of the equation. By substituting these identities, one can demonstrate the equality effectively. It is recommended to minimize the use of trigonometric functions for clarity.

PREREQUISITES
  • Understanding of trigonometric identities, specifically sin(3θ) and cos(2θ).
  • Familiarity with algebraic manipulation of trigonometric expressions.
  • Knowledge of sine and cosine functions and their properties.
  • Ability to simplify expressions using substitution techniques.
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  • Study the derivation and applications of the sine and cosine double angle identities.
  • Learn how to expand and simplify trigonometric functions using identities.
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Students, educators, and anyone studying trigonometry or preparing for calculus, particularly those interested in simplifying trigonometric expressions and solving equations.

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can someone please show me why sinxcos2x = (sin3x - sinx)*0.5

I've been working on it for thirty minutes
 
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can u expand sin(3x) ?? and cos(2x)

just simplify both sides..and u'll get it..
 


You should use the identities

[tex]\cos{2\theta} = 1-2\sin^2{\theta}[/tex]

[tex]\sin{3\theta} = 3\sin{\theta} - 4\sin^3{\theta}[/tex]

Perhaps you were putting these identities in terms of cosines. When possible, stick with as few trig functions as possible and replace the [tex]\cos^2{\theta}[/tex] with [tex]1-\sin^2{\theta}[/tex] or vice versa.
 
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