Math trigonometric questions? 1)Determine tan2θ if sinθ + cosθ = -1 2) Express sin2θ in terms of csc θ and sec θ 3) Express cos3θ in terms of sin θ
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Originally Posted by crosser43 Math trigonometric questions? 1)Determine tan2θ if sinθ + cosθ = -1 2) Express sin2θ in terms of csc θ and sec θ 3) Express cos3θ in terms of sin θ 1) sinθ + cosθ = -1 sinθ + cosθ + 1 = 0 2sin(0.5θ)cos(0.5θ) + 2cos^2(0.5θ) = 0 2*cos(0.5θ)[sin(0.5θ) + cos(0.5θ)] = 0 cos(0.5θ) = 0 or 0.5θ = 0.5π or θ = π sin(0.5θ) + cos(0.5θ) = 0 tan(0.5θ) = -1 or 0.5θ = 0.25π or 2θ = π
Hello crosser43 Originally Posted by crosser43 Math trigonometric questions? 1)Determine tan2θ if sinθ + cosθ = -1 Square both sides: Now use the identities and : 2) Express sin2θ in terms of csc θ and sec θ 3) Express cos3θ in terms of sin θ See line 40 of Multiple-Angle Formulas -- from Wolfram MathWorld, and put Grandad
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