Answer:
a) 90°
b) (d) The angle at the circumference in a semicircle is a right angle
Step-by-step explanation:
An inscribed angle has half the measure of the arc it subtends.
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Angle ABC is inscribed in a semicircle and subtends an arc of 180°, so has a measure of 180°/2 = 90°. Here, that observation is described by ...
The angle at the circumference in a semicircle is a right angle
