AP EAMCET · Maths · Trigonometric Equations

If $x = \log_{e} [\cot (\frac{π}{4} + θ)]$ and $θ \in (\frac{- π}{4}, \frac{π}{4}),$ then consider the following statements: $I : \cosh x = \sec 2 θ$
$II :$ $\sinh x = - \tan 2 θ$ Then which one of the following options is true?

A $I$ is true and $II$ is false
B $I$ is false and $II$ is true
C Both $I$ and $II$ are true
D Both $I$ and $II$ are false

Verified Solution

Answer & Solution

Correct Answer

(C) Both $I$ and $II$ are true

Step-by-step Solution

Detailed explanation

Given, x=logecotπ4+θ ⇒ex=cotπ4+θ =cosθ-sinθcosθ+sinθ Now, coshx=ex+e-x2 =ex+1ex2 =12cosθ-sinθcosθ+sinθ+cosθ+sinθcosθ-sinθ…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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If x=logecotπ4+θ and θ∈-π4,π4, then consider the following statements: I: coshx=sec2θII: sinhx=-tan2θ Then which one of the following options is true?

Step-by-step Solution

If $x = \log_{e} [\cot (\frac{π}{4} + θ)]$ and $θ \in (\frac{- π}{4}, \frac{π}{4}),$ then consider the following statements: $I : \cosh x = \sec 2 θ$
$II :$ $\sinh x = - \tan 2 θ$ Then which one of the following options is true?