prove that line joining the midpoint of 2 equal chords substain equal angle with the chord?

Azlaan,

The basic ideas you will need:

Draw a reasonably accurate diagram.
Look for a symmetry.
Add some appropriate extra lines.
Label sets of segments that are congruent:
-things stated to be equal
-halves of something
-radii of a circle

Good Hunting!
-RD

Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.