Trigonometry · Intermediate · 5 min
Radians
Radians measure how many radius-lengths fit along an arc.
WHAT HAPPENS IF…How long is a half-circle arc of radius 2?
Loading the mathematical model…
A full circumference is 2πR. Dividing by R gives 2π radians per full turn, independently of radius. Degree and radian measures are related by 180°=π radians. The arc-length formula s=Rθ assumes θ is measured in radians.
A detail that matters
s=Rθ does not work directly with a degree number.
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