Twelve > Parabola
Find the parametric equation of the parabola (y - 2)2 = 2(x + 3).
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Solution
The parametric equation of the parabola $\rm ( y - k)^2 = 2 ( x - h)$ is $\rm (x,y) = (h + at^2, k + 2at)$.
We compare the given equation of the parabola $\rm (y - 2)^2 = 2 (x + 3)$ with $\rm ( y - k)^2 = 2 ( x -h)$, we get,
$\rm (h,k) = (-3, 2)$ and $\rm a = \frac{2}{4} = \frac{1}{2}$
Now, we solve for the value of x,
$\rm x = h + at^2$
$\rm or, x = -3 + \frac{1}{2} t^2$
And, we solve for the value of y,
$\rm y = k + 2at$
$\rm or, y = 2 + 2 \cdot \frac{1}{2} \cdot t$
$\rm \therefore y = 2 + t$
Hence, the required parametric equation of the parabola $\rm ( y - 2)^2 = 2 (x + 3)$ is $\rm x = -3 + \frac{1}{2} t^2$ and $\rm y = 2 + t$.
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