How do you find the parametric equations for the rectangular equation x^2+y^2-25=0 ?

Since ${x}^{2} + {y}^{2} - 25 = 0$ is the equation of the circle centered at the origin with radius 5, its corresponding parametric equations are
$x \left(t\right) = 5 \cos t$
$y \left(t\right) = 5 \sin t$,
where $0 \le q t < 2 \pi$.