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ECAT Mathematics QUESTION #771
Question 1
If \(x = a\cos\theta,\ y = a\sin\theta\), then \(\dfrac{dy}{dz} = ?\)
  • \(-\cot\theta\)✔️
  • \(\cos\theta\)
  • \(\tan\theta\)
  • None
Correct Answer Explanation
\(\dfrac{dx}{d\theta} = -a\sin\theta,\ \dfrac{dy}{d\theta} = a\cos\theta\), so \(\dfrac{dy}{dx} = \dfrac{a\cos\theta}{-a\sin\theta} = -\cot\theta\).