Question

Please help me if you can!

Answer 1

arc ACD = 120°

Explanation:

Angle ACD = 120°

From cyclic quadrilaterals, opposite angles are supplementary.

angle ABD + angle ACD = 180

120 + ACD = 180

ACD = 60

Let the centre be point O.

Then arc ACD is the same as the angle AOD

From chord properties,

angle ABD = angle AOD /2

or

AOD = 2 * ABD = 2*60 = 120°