Now I will show you another unit of angle measurement--- radian On radian is an angle formed when you move the terminal side a distance equal to 1 radius of the circle. Since the circumference of a circle is `2πtimesr` That means if we move the terminal side `2π` times the length of the radius ,we will go back to the initial position. or we can say `2π` radian = `360` degree than we get