Q how to bisect an angle?

Answer 1

I assume you mean with a compass and straightedge (ruler).

Refer to the figure at
http://etc.usf.edu/clipart/32400/32417/_32417_lg.gif

Put the point of the compass at the vertex (B in the figure) and draw arc 1 through both sides of the angle. Then, using a shorter fixed radius for the compass, and putting he point of the compass at the places where arc 1 interects the sides of the angle, draw arcs 2 and 3 so that they intersect.

Then draw the line through the vertex and the points where arcs 2 and 3 intersect. It will bisect the angle.