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| Question 1003087:  Use trigonometric identities to solve tan(2θ)+tan(θ)=0 exactly for 0≤θ≤π.
 Answer by Alan3354(69443)
      (Show Source): 
You can put this solution on YOUR website! Use trigonometric identities to solve tan(2x)+tan(x)=0 exactly -----------
 tan(2x) = 2tan(x)/(1 - tan^2(x))
 --> 2tan(x)/(1 - tan^2(x)) + tan(x) = 0
 tan(x) = 0
 --> x = 0, pi
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 2/(1 - tan^2(x)) + 1 = 0
 2/(1 - tan^2(x)) = -1
 (1 - tan^2(x))/2 = -1
 1 - tan^2(x) = -2
 tan^2(x) = 3
 x = sqrt(3)
 --> x = pi/3, 4pi/3
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 x = -sqrt(3)
 --> x = 2pi/3, 5pi/3
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 That's theta from 0 to 2pi.  If you only want up to pi eliminate the others.
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