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A hint to get started

Eliminate trigonometric parameters to identify an ellipse

Find the Cartesian equation of x=8cos⁡θx=8\cos\theta, y=4sin⁡θy=4\sin\theta, 0≤θ≤2π0\le\theta\le2\pi.

CJC · Lecture · Example 5

Divide each coordinate by its amplitude and use sin²+cos²=1.

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