(i) East and west directions form an angle of 180Ëš, which is a straight angle.
(ii) East and north directions form an angle of 90Ëš, which is a right angle.
(iii) North and north-east directions form an angle of 45Ëš, which is an acute angle.
(iv) North and south-east directions form an angle of 135Ëš, which is an obtuse angle.