Arc Length and Radians
r
2r =D
r =radiusD =diameterC =circumfrance
C
D=π =3.14159
C2r
=π
C =2πrC2π
=r
C2π
=Sθ=r
S =rθθ is measured in radians
θ =2π
S = r2π = C
2π rad = 360o
1rad =360o
2π= 57.3deg
rad
Small Angle ApproximationSmall-angle approximation is a useful simplification of the laws of trigonometry
which is only approximately true for finite angles.
FOR θ ≤10o
10o =0.174532925 radians
sinθ ; θ
sin(10o ) =0.173648178
EXAMPLE