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tan2 θ1 + tan2 θ\dfrac{\text{tan}^2 \text{ θ}}{\text{1 + tan}^2 \text{ θ}} is equal to

  1. 2sin2 θ

  2. 2cos2 θ

  3. sin2 θ

  4. cos2 θ

Trigonometric Identities

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Answer

Given, tan2 θ1 + tan2 θ\dfrac{\text{tan}^2 \text{ θ}}{\text{1 + tan}^2 \text{ θ}}

On solving,

sin2 θcos2 θ1+sin2 θcos2 θsin2 θcos2 θcos2 θ+sin2 θcos2 θsin2 θ cos2 θcos2 θ(cos2 θ+sin2 θ)sin2 θ.\Rightarrow \dfrac{\dfrac{\text{sin}^2 \text{ θ}}{\text{cos}^2 \text{ θ}}}{1 + \dfrac{\text{sin}^2 \text{ θ}}{\text{cos}^2 \text{ θ}}} \\[1em] \Rightarrow \dfrac{\dfrac{\text{sin}^2 \text{ θ}}{\text{cos}^2 \text{ θ}}}{\dfrac{\text{cos}^2 \text{ θ} + \text{sin}^2 \text{ θ}}{\text{cos}^2 \text{ θ}}} \\[1em] \Rightarrow \dfrac{\text{sin}^2 \text{ θ} \text{ cos}^2 \text{ θ}}{\text{cos}^2 \text{ θ} (\text{cos}^2 \text{ θ} + \text{sin}^2 \text{ θ})} \\[1em] \Rightarrow \text{sin}^2 \text{ θ}.

Hence, Option 3 is the correct option.

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