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Geometrically, the point in the Cartesian plane with coordinates

x=\frac{a}{c},\quad y=\frac{b}{c}

is on the unit circle x2 + y2 = 1. In this equation, the coordinates x and y are given by rational numbers. Conversely, any point on the unit circle whose coordinates x, y are rational numbers gives rise to a primitive Pythagorean triple.

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