The measure of angle a is 70 degrees
How to determine the measure of a?
The angle in a semicircle is a right angle.
This means that:
a + d = 90
Where O is the center of the circle
From the figure, we have:
Angle d and the angle with a measure of 20 degrees are corresponding angles
This means that
d = 20
Substitute d = 20 in a + d = 90
a + 20 = 90
Subtract 20 from both sides of the equation
a = 70
Hence, the measure of angle a is 70 degrees
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