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The gon is a measurement of plane angles, corresponding to 1/400 of a full circle, thus dividing a right angle in 100. The unit is also known as the grad or grade. One gon is equal to 9/10 of a degree or π/200 of a radian.

The unit originated in France as the grade, as part of the all metric system. Due to confusion with existing grad(e) units of northern Europe, the name gon was adopted. In Germany, the unit is also known as the Neugrad (new degree).

Although attempts at a general introduction was made, the unit was really only adopted in some countries and for specialized areas, like land measurement. The familiar degree (1/360 circle) or the mathematically convenient SI unit of angle, the radian (1/2π of a circle), are generally used instead of the gon.

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