Name: Amy
Who is asking: Student
Question:
If you have an angle you can measure its size in the following way. Draw a unit circle (circle with radius 1) with center at the vertex of the angle. Measure the length of the arc (counterclockwise) subtended by the angle (the length of the orange arc in the diagram). Suppose that this length is t, then we say that the radian measure of the angle is t radians. Since the circumference of the unit circle is 2 pi, the 360^{o} angle has radian measure of 2 pi. Likewise 180^{o} is pi radians (half way around the circle). 90^{o} is ^{pi}/_{2} radians and 45^{o} is ^{pi}/_{4}. For other angles I remember that One last point is that if you measure the arc clockwise then the radian measure is negative. Thus 45^{o} is ^{pi}/_{4} radians. Cheers,Harley
