Question

Find the Cartesian equation of the circle whose parametric equations are x = 3 cos θ, y = 3 sin θ, 0 ≤ θ ≤ 2π.

Answer 1

Given x = 3 cos θ, y = 3 sin θ

Now x² + y² = 9 cos²θ + 9 sin²θ

x² + y² = 9 (cos²θ + sin²θ)

x² + y² = 9 which is the Cartesian equation of the required circle.