ann1ahilladiyanna ann1ahilladiyanna
  • 21-11-2016
  • Mathematics
contestada

show that cos(3theta) = cos^3(theta)-3 cos(theta)sin^2(theta) ... use this to find an equation in rectangular coordinates for the curve r= 4 cos (3theta)......


ANY HELP ? ...?

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syed514
syed514 syed514
  • 23-11-2016
First, the angle sum forumlas:sin(α+β)=sinαcosβ+sinβcosαcos(α+β)=cosαcosβ−sinαsinβSo,cos(3θ)=cos(2θ+θ)=cos(2θ)cosθ−sin(2θ)sinθ=(cos2θ−sin2θ)cosθ−(2sinθcosθ)sinθ
From there, it's distribute and simplify...
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