angles equations

acute angles

between 0 and π/2 radians

obtuse angles

between π/2 and π radians

radian measure

θ=l/r; l=length, r=radius

length of a circular arc

l=θ*r; theta must be in radians (arc length)

coterminal angle

θc=θ+2πk; k=any integer

arc length

l=θ/2π*C (radians), l=θ/360*C (degrees); l=length, C=circumference of the circle

sector area

a=θ/2π*A (radians), a=θ/360*A (degrees); A=area of the circle