Question

How to state the quadrant in which an angle lies in radians?

Answer 1

Quadrant I is 0 to 90 degrees. In radians, that's 0 to pi/2

Quadrant II is 90 to 180 degrees. In radians, that's pi/2 to pi

Quadrant III is 180 to 270 degrees. In radians, that's pi to 3pi/2

Quadrant IV is 270 to 360 degrees. In radians, that's 3pi/2 to 2pi.

Its best to just memorize this, but if you need it, the conversion from degrees to radians is d*180/pi, where d is the degree of the angle. In the case that you get a negative angle or an angle that is greater than 360 degrees, just add or subtract 360 degrees until you get an angle that is within 0 to 360 degrees.