In circle O, AC and BD are diameters.

Circle O is shown. Line segments B D and A C are diameters. A radius is drawn to cut angle C O C into 2 equal angle measures of x. Angles A O C and B O C also have angle measure x.

What is mArc A B?

72°
108°
120°
144°

mArc A B = 120° (C)

Step-by-step explanation:

Question:

In circle O, AC and BD are diameters.

Circle O is shown. Line segments B D and A C are diameters. A radius is drawn to cut angle D O C into 2 equal angle measures of x. Angles A O D and B O C also have angle measure x.

What is mArc A B?

a)72°

b) 108°

c) 120°

d) 144°

Solution:

Find attached the diagram of the question.

Let P be the radius drawn to cut angle D O C into 2 equal angle measures of x

From the diagram,

m Arc AOC = 180° (sum of angle in a semicircle)

∠AOD + ∠DOP + ∠COP = 180° (sum of angles on a straight line)

x° +x° + x° =180°

3x = 180

x = 180/3

x = 60°

m Arc DOB = 180° (sum of angle in a semicircle)

∠AOB + ∠AOD = 180° (sum of angles on a straight line)

∠AOB + x° = 180

∠AOB + 60° = 180°

∠AOB = 180°-60°

∠AOB = 120°

mArc A B = 120°

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