Draw a line l. Draw a perpendicular to l at any point on l. On this perpendicular choose a point X, 4 cm away from l. Through X, draw a line m parallel to l.
To construct: A line parallel to given line when perpendicular line is also given.
Steps of construction:
(a) Draw a line l and take a point P on it.
(b) At point P, draw a perpendicular line n with the help of a protractor.
(c) Take PX = 4 cm on line n.
(d) At point X, again draw a perpendicular line m with the help of a protractor.
It is the required construction.