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A circle is centered on point B. Points A, C and D lie on its circumference.

If ZABC measures 40°, what does ZADC measure?

A circle is centered on point B. Points A, C and D lie on its circumference. If ZABC-example-1
User Fiore
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1 Answer

2 votes

Given:

A circle is centered on point B.

Points A, C and D lie on its circumference.

If
m\angle ABC measures 40°.

To find:

The
m\angle ADC.

Solution:

Central angle theorem: According to this theorem, the central angle is equal to the twice of inscribed angle on the same intercepted arc.

In the given figure
\angle ABC is the central angle and
m\angle ADC is the inscribed angle on the same arc AC.

Using central angle theorem, we get


m\angle ABC=2m\angle ADC


40^\circ=2m\angle ADC


(40^\circ)/(2)=m\angle ADC


20^\circ=m\angle ADC

Therefore, the measure of angle ADC is 20°.

User EFeit
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