In the given figure A, B, C, D are points on the circle such that <acb=400
and <dab=60^{0
 what is the measure of <dba}

solution
<acb=<adb=40⁰  (angles on same segment)
in triangle dba,
<dab=60⁰
<adb=40^o
therefore, <dba= 180-(60+40)
                         =80^o