Question

A circle is centered on point B. Points A, C and D lie on its circumference. If ADC measures 20º, what does /ABC measure?

Answer 1

Given:

m∠ADC = 20º

To find m∠ABC, we have:

From the figure above, we can see that angle ADC is the inscribe angle, and an ABC is the intercepted arc.

We know that an intercepted arc is twice the inscribed angle.

We have:

m∠ABC = 2(m∠ADC)

m∠ABC = 2(20)

m∠ABC = 40º

ANSWER:

40º