1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Simplify sin3θ

  1. Mar 25, 2010 #1
    1. The problem statement, all variables and given/known data
    Simplify Sin[3θ] (no double angles)

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

    3. 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 dont have the formula i need or what.
  2. jcsd
  3. Mar 25, 2010 #2


    User Avatar
    Homework Helper

    Sin2θ = 2sinθcosθ, remember that one?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Simplify sin3θ
  1. Simplifying Factorials (Replies: 2)

  2. Simplifying a summation (Replies: 10)

  3. Simplifying a fraction (Replies: 2)