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प्रश्न
An equilateral triangle is inscribed in the parabola y2 = 4ax whose one vertex is at the vertex of the parabola. Find the length of the side of the triangle.
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उत्तर
As shown in the figure APQ denotes the equilateral triangle with its equal sides of length l (say).

Here AP = l
So AR = l cos30°
= `l sqrt(3)/2`
Also, PR = `l sin 30^circ = l/2`.
Thus `(lsqrt(3))/2, l/2` are the coordinates of the point P lying on the parabola y2 = 4ax.
Therefore, `l^2/4 = 4a (lsqrt(3))/2`
⇒ `l = 8 asqrt(3)`.
THus, 8 `asqrt(3)` is the required length of the side of the equilateral triangle inscribed in the parabola y2 = 4ax.
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