Question

AB IS THE DIAMETER OF THE CIRCLE AND DE IS A CHORD PARALLEL TO AB. IF ANGLE BAC=20 FIND ANGLE ADC

Answer 1

Let’s the center of circle will be named O. So, ˂COB=2˂CAB=40° (because ˂COB is central angle, ˂CAB is inscribed angle and they are based on one arc). ˂COA=180°-˂COB=140° (because they are interconnecting).
˂ADC = 180° - ˂COA = 40°
Answer: ˂ADC = 40°