Step 1: Draw a circle with center O and radius 4 cm.
Step 2: Draw any diameter AOB of the circle.
Step 3: At A, draw ∠OAX = 90 . Produce XA = Y
Step 4: At B, draw ∠OBX' = 90 . Produce X' B to Y'.
Here, XAY and X'BY' are the tangents to the circle at the end points of the diameter AB