Question 1124443
From what you did I can determine that you've had the right picture of all stuffs. Therefore I do not need to draw again.
First we know angle AOC=angle BOD=90 degrees.
Therefore angle AOC-angle BOC=angle BOD-angle BOC
angle AOB=angle COD. 
And we're pretty much done. You see, simply make use of the equations you have and apply the properties.