Circle theorems question

Attachment 24926
Can anyone please explain to me how to get the missing answers? Thanks.

(just click on the pic to zoom in)

I found out ABC, but I can't figure out OAD.

value of angles
RCB =56
ABC=70.5
OAD=OAC + DCT
CAD =DCT
Triangle OAC is isosceles.Finish it after finding angleAOC

How is ABC 70.5?

Quote:

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Originally Posted by Ashir

How is ABC 70.5?

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Its 1/2 of 141

And? Opposite angles add up to 180 is the theory. Therefor ABC is 39. Why would it be one half of 141?
And I checked, my answers were right.

if angle ADC =141 arc ADC =78,angle AOC =78 not obtuse as you show. I assumed that arc ADC =141

What arc?

Still in need of an answer.

angleOAD = 74 deg Ichanged your drawimg moving A closer to C making angle AOC acute