Answer the following questions on angle measure.
(a) What is meant by saying that an angle is measured in radians? Explain with reference to a circle of radius 1 unit.
(b) A complete rotation about a point subtends an angle of 360∘. Explain why the same rotation is equal to 2π when the angle is expressed in radians.
(c) From the result of part (b), explain how one may obtain a relation between any degree measure D∘ and its radian measure Rrad.
(d) Without quoting any ready–made conversion formula, determine the radian measure of 135∘ and the degree measure of 2.4rad, showing each step clearly.