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Mathematics

The value of (1 + tan θ + sec θ)(1 + cot θ − cosec θ) is:

  1. −4

  2. −1

  3. 1

  4. 2

Trigonometric Identities

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Answer

Given,

(1 + tan θ + sec θ)(1 + cot θ − cosec θ)

(1+sinθcosθ+1cosθ)(1+cosθsinθ1sinθ)(cosθ+sinθ+1cosθ)(sinθ+cosθ1sinθ)(cosθ+sinθ)212cosθsinθcos2θ+sin2θ+2sinθcosθ1cosθsinθ1+2sinθcosθ1cosθsinθ2sinθcosθcosθsinθ2.\Rightarrow \Big(1 + \dfrac{\sin \theta}{\cos \theta} + \dfrac{1}{\cos \theta}\Big) \Big(1 + \dfrac{\cos \theta}{\sin \theta} - \dfrac{1}{\sin \theta}\Big)\\[1em] \Rightarrow \Big( \dfrac{\cos \theta + \sin \theta + 1}{\cos \theta} \Big) \Big(\dfrac{\sin \theta + \cos \theta - 1}{\sin \theta} \Big)\\[1em] \Rightarrow \dfrac{(\cos \theta + \sin \theta)^2 - 1^2}{\cos \theta \sin \theta} \\[1em] \Rightarrow \dfrac{\cos^2 \theta + \sin^2 \theta + 2\sin \theta \cos \theta - 1}{\cos \theta \sin \theta} \\[1em] \Rightarrow \dfrac{1 + 2\sin \theta \cos \theta - 1}{\cos \theta \sin \theta} \\[1em] \Rightarrow \dfrac{ 2\sin \theta \cos \theta}{\cos \theta \sin \theta} \\[1em] \Rightarrow 2.

Hence, option 4 is the correct option.

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