How did they come to this parameterization of an ellipse?

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The topic is about line integrals, the question:

Calculate $\int_\gamma \vec x \cdot d\vec s$ for

$\vec v = (0,xy^2)$ and $\gamma$ die ellipse with the equation $x^2+(y/2)^2=1$ once to go counter clockwise

then they give the answer for the parameterization as:

$\gamma :[0, 2\pi]\to \Bbb R^2, t \to (\cos t, 2 \sin t)$

my question is, how did they find the parameterization to be $(\cos t , 2 \sin t)$