(i) Define the degree measure of an angle and the radian measure of an angle.
(ii) State the general relation connecting the degree measure θdeg and the radian measure θrad of the same angle.
(iii) Without performing any calculations, write down the radian measures corresponding to the following standard angles:
(a) 30∘ (b) 45∘ (c) 60∘ (d) 90∘ (e) 180∘.