Simplifying Sin[3θ] to Simplifying Trigonometric Expressions

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SUMMARY

The discussion focuses on simplifying the trigonometric expression Sin[3θ] using the angle addition formula and known identities. The key equations utilized include Sin[3θ] = Sin[θ + 2θ] and the expansion Sin[α + β] = Sin[α] Cos[β] + Cos[α] Sin[β]. The simplification process leads to the established identity Sin[3θ] = 3sinθ - 4sin^3 θ, which is derived through the application of Sin[2θ] = 2sinθcosθ and Cos[2θ] = 1 - 2Sin^2θ. The discussion highlights the importance of recognizing and applying these fundamental trigonometric identities.

PREREQUISITES
  • Understanding of trigonometric identities, specifically Sin[α + β] and Sin[2θ]
  • Familiarity with the concept of angle addition in trigonometry
  • Knowledge of polynomial expressions involving sine functions
  • Basic algebraic manipulation skills
NEXT STEPS
  • Study the derivation of Sin[3θ] using the angle addition formula in detail
  • Learn about the application of double angle formulas in trigonometric simplifications
  • Explore polynomial identities involving sine and cosine functions
  • Practice additional trigonometric simplifications using various identities
USEFUL FOR

Students studying trigonometry, educators teaching trigonometric identities, and anyone looking to enhance their skills in simplifying trigonometric expressions.

Confusingmeh
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Homework Statement


Simplify Sin[3θ] (no double angles)

Homework Equations


Sin[3θ]=Sin[θ+2θ]
Sin[α + β] = Sin[α] Cos[β] + Cos[α] Sin[β]
Sin[3θ] = 3sinθ - 4sin^3 θ
Cos2θ = 1-2Sin^2θ

The Attempt at a Solution


Sin[3θ] = sin[θ+2θ]
Sin[θ+2θ] = Sinθ Cos2θ + Cosθ Sin2θ
Sinθ Cos2θ + Cosθ Sin2θ = Sinθ (1-2Sin^2θ) + Cosθ Sin2θ
=Sinθ - 2Sin^3θ + Cosθ Sin2θ This is where i get lost...I know it should end up being
= (3sinθ - 4sin^3 θ) but i cannot figure out how to get there. I don't know whether I just don't have the formula i need or what.
 
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Sin2θ = 2sinθcosθ, remember that one?
 

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