> The radians became popular in the 19th century Something akin to radians was widely used in ancient India. That is, sine tables constructed for a circle with

> The radians became popular in the 19th century Something akin to radians was widely used in ancient India. That is, sine tables constructed for a circle with circumference 360·60 (angular minutes) and radius 3438 ≈ 360·60/2π. In Europe, radians per se developed in the early 18th century. What is true is that the name radian came about in the late 19th century. > trigonometric functions with arguments in radians are harmful Trigonometric functions are not inherently "harmful", but they are sometimes cumbersome. Changing the units doesn't make all that much practical difference. Avoiding transcendental functions in favor of vector methods is often a good strategy though, especially in code.