Construction of Bisecting Angles
Using a protractor draw are angle of measure 80^{0}.Bisect the given angle.
Step 1: Draw a ray OA.
Step 2:With the help of protractor draw an angle AOB of measure 80^{0}
Step 3: With center O and a convenient radius draw an arc cutting arms OA and OB at P and Q respectively.
Step 4: With center P and radius more than half-length of PQ, draw an arc.
Step 5: With center Q and same radius as in the step 4, draw another arc intersecting the arc drawn in the step 4 at R.
Step 6: Join OR and Produce it to form a ray OX the angle AOX is the angle of measure 40^{0} ( one half of 80^{0})
Construction of Angles 60^{0},120^{0}and 180^{0}
Step 1 : Draw a line segment AB of any length.
Step 2 : Draw an arc of any radius with center A, which cuts AB
at P.
Step 3 : With same radius and center at P draw another arc,
which cuts earlier arc at Q.
Step 4 : Join AQ.
Step 5 : ∠BAD = 60^{0}
Step 4 : With same radius and centre at Q draw another arc
which cut the first arc at R.