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lf \( \Large X=9\cos \theta \ and\ y=7\sin \theta \) then find the value of \( \Large \frac{x^{2}}{81}+\frac{y^{2}}{49} \)

A) 1
B) \( \Large \frac{49}{81} \)
C) \( \Large \frac{81}{49} \)
D) \( \Large 1+\tan^{2} \theta \)

Correct Answer:

A) 1

Description for Correct answer:
\( \Large x=9\cos \theta ,\ y=7\sin \theta \)

\( \Large \frac{x^{2}}{81}+\frac{4^{2}}{49} = \frac{ \left(9\cos \theta \right)^{2} }{81}+\frac{ \left(7\sin \theta \right)^{2} }{49} \)

=\( \Large \frac{81\cos^{2} \theta }{81}+\frac{49sin^{2} \theta }{49} \)

=\( \Large \cos^{2} \theta + \sin^{2} \theta = 1 \)

Part of solved Trigonometry questions and answers : >> Elementary Mathematics >> Trigonometry

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