Page 33 - Calculus Demystified

20
y CHAPTER 1 Basics

α

x

positive angle

Fig. 1.26

y

α x

negative angle

Fig. 1.27

◦
In degree measure, one full rotation about the unit circle is 360 ; in radian
measure, one full rotation about the circle is just the circumference of the circle or
2π. Let us use the symbol θ to denote an angle. The principle of proportionality
now tells us that
degree measure of θ radian measure of θ
= .
360 ◦ 2π
In other words
π
radian measure of θ = · (degree measure of θ)
180
and
180
degree measure of θ = · (radian measure of θ).
π