Answer:
Bisecting an angle
Step-by-step explanation:
David first draw an angle CAB i.e 
Then draw an arc cutting AC at D and AB at E .
With E as centre , draw an arc then with D as centre draw an arc
Both the arcs will intersect at some point .
If we join point A to this intersecting point , we get an angle bisector of 
So, based on the markings that are present , he is actually bisecting the angle.
An angle bisector is a line or line segment which bisects an angle into two equal parts .