ઉપવલય \(\frac{x^{2}}{a^{2}}+\frac{y^{2}}{4}=1\), a \(>2\), ની અંતર્ગત, જેનું એક શિરોબિંદુ આ ઉપવલયની મુખ્ય અક્ષનું એક અંત્ય બિંદુ હોય અને જેની એક બાજુ \(y\)-અક્ષને સમાંતર હોય તેવા ત્રિકોણનું મહત્તમ ક્ષેત્રફળ \(6 \sqrt{3}\) છે. તો આ ઉપવલયની ઉત્કેન્દ્રતા ....... છે,

A \(\frac{\sqrt{3}}{2}\)
B \(\frac{1}{2}\)
C \(\frac{1}{\sqrt{2}}\)
D \(\frac{\sqrt{3}}{4}\)

Verified Solution

Answer & Solution

Correct Answer

(A) \(\frac{\sqrt{3}}{2}\)

Step-by-step Solution

Detailed explanation

\(A=\frac{1}{2} a(1-\cos \theta)(4 \sin \theta)\) \(A =2 a (1-\cos \theta) \sin \theta\) \(\frac{ dA }{ d \theta}=2 a \left(\sin ^{2} \theta+\cos \theta-\cos ^{2} \theta\right)\) \(\frac{ dA }{ d \theta}=0 \Rightarrow 1+\cos \theta-2 \cos ^{2} \theta=0\)…

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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