Gradian (gon)
The gradian, also known as gon or grad, was established in France following the French Revolution to promote a decimal-based system of angular measurement. In this system, a circle is divided into 400 gradians, resulting in a right angle measuring exactly 100 gradians. The gradian aimed to make calculations easier by matching the decimal metric system. While it did not gain universal acceptance, it remains in use within certain engineering and surveying practices, especially in France and parts of Central Europe. Its straightforward decimal approach is convenient, but degrees and radians are more widely used globally.
Radian (rad)
The radian, symbol rad, is the standard SI unit for measuring angles. It was introduced in the 18th century by mathematicians who sought a natural, dimensionless unit for angle measurement. One radian represents the angle created when the arc length of a circle equals the circle’s radius; therefore, a full circle contains exactly 2π radians, which is approximately 6.283 radians. This makes it fundamental in trigonometry, calculus, and physics, where radians simplify formulas involving angular velocity, periodic motion, and wave functions. Unlike degrees, which divide the circle into 360 parts, radians connect directly to the geometry of a circle, making them the preferred unit in mathematics, science, and engineering worldwide.