Answer:
Explanation:
The rule required here is that the measure of an inscribed angle is half the measure of the arc it intercepts.
(a) ∠BCD = 90°, so arc BAD is ...
... x + 60° = 2×90°
... x = 180° -60° = 120°
(b) ∠ABC = 100°, so arc ADC is ...
... x + y = 2×100°
... y = 200° -120° = 80°
(c) From part A, we know that arc BAD = 180°, so arc BCD = 180° (since they add to make 360°). Arc BCD is ...
... y + z = 180°
... z = 180° -80° = 100°