The measure of ∠angle B when Angle C is inscribed in circle O and AB is a diameter of circle O, is 19 degrees.
According to the triangle angle sum theorem, the sum of all the angle(interior) of a triangle is equal to the 180 degrees.
In the image attached below:
The measure of the angle A is,
[tex]m\angle A=71^o[/tex]
The measure of the angle C in a semicircle is,
[tex]m\angle C=90^o[/tex]
The sum of all the angle(interior) of a triangle is equal to the 180 degrees. Thus,
[tex]\angle A+\angle B+\angle C=180\\90+\angle B+71=180\\\angle B=180-90-71\\\angle B=19^o[/tex]
Thus, the measure of ∠angle B when Angle C is inscribed in circle O and AB is a diameter of circle O, is 19 degrees.
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