You can use any angular measure—radians, degrees, or revolutions—in some of the equations in Chapter 9, but you can use only radian measure in others. Identify those for which using radians is necessary and those for which it is not, and in each case give your reasoning.

Solution 19DQ Step 1: In the radian system of angular measurement.the measure of one revolution is 2. The arc-length is given by only rf measured in radians.we know that the circumference of a circle is given by 2r.so if we define radians such that 360 is 2 then we get for the value of arc-lengths: A = 2r /2 = v/s degrees A = 2r /360 = 0 2/360 . * R * R* Step 2: Degrees and radians are not arbitrary units of measure because angles are unitless.as pseudo-units,rad is the value 1 (unitless) and degrees-sign is the value /180 .