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If cosθ + sec θ = 6 , find the value of cos3θ + sec3θ . |
218 198 234 200 |
198 |
Formula I → [ secθ = \(\frac{1}{cosθ}\)] Formula II → [If x + \(\frac{1}{x}\) = n and x3 + \(\frac{1}{x^3}\) = n3 - 3n] cosθ + \(\frac{1}{cosθ}\) = 6 ⇒ cos3θ + \(\frac{1}{cos^3θ}\) = (6)3 - 3 × 6 ⇒ cos3θ + sec3θ = 216 - 18 = 198 |
