Radian (rad)
Definition: A radian (symbol: rad) is a unit of angle in the International System of Units (SI). It is defined as the angle subtended at the center of a circle by an arc equal in length to the radius of the circle. One radian is approximately equal to 57.2958 degrees.
History/origin: The concept of the radian was developed in the early 18th century. The term "radian" was first used in print in 1873 by James Thomson. It became the standard unit of angular measure in mathematics and physics.
Current use: The radian is used globally in mathematics, physics, and engineering. It is the standard unit of angular measure in calculus and trigonometry, as it simplifies many formulas.
Degree (°)
Definition: A degree (symbol: °) is a unit of angle in the imperial and US customary systems of measurement. It is defined as 1/360 of a full rotation. One degree is equal to π/180 radians.
History/origin: The degree has been used as a unit of angle since ancient times. It was originally based on the Babylonian sexagesimal system, which used a base-60 number system. The modern degree was standardized in the 18th century.
Current use: The degree is primarily used in everyday life, navigation, and various fields such as astronomy, geography, and surveying. It is also used in many engineering applications.