Arcs and Angles in Circles

What is the radius of a circle whose equation is x²+y²+8x−6y+21=0?

• 2 units

• 3 units

• 4 units

• 5 units

What is the radius of a circle whose equation is (x – 7)² + (y – 10)² = 4?

• 2 units

• 4 units

• 8 units

• 16 units

What is the center of a circle represented by the equation (x−5)²+(y+6)²=4²?

• (-6, 5)

• (-5, 6)

• (5, -6)

• (6, -5)

What is the center of a circle represented by the equation (x+9)²+(y−6)²=10²?

• (-9, 6)

• (-6, 9)

• (6, -9)

• (9, -6)

Which equation represents the general form a circle with a center at (–2, –3) and a diameter of 8 units?

• x² + y² + 4x + 6y – 51 = 0

• x² + y² – 4x – 6y – 51 = 0

• x² + y² + 4x + 6y – 3 = 0

• x² + y² – 4x – 6y – 3 = 0

Two circles are concentric if they have the same center. Which equation represents a circle that is concentric with the circle shown but has a radius that is twice as large?

• (x – 4)² + (y – 6)² = 4

• (x – 4)² + (y – 6)² = 16

• (x – 6)² + (y – 4)² = 16

• (x – 6)² + (y – 4)² = 4

What is the measure of angle COA?

• 140°

• 150°

• 160°

• 170°

Points D, E, and F are on circle C and EF ≅ DF. What is the measure of ∠CDF?

• 14°

• 19°

• 26°

• 38°

Points A, B, C, and D lie on circle M. Line segment BD is a diameter. The measure of arc CD equals the measure of arc DA. What is the measure of angle ADM?

• 22.5°

• 30.0°

• 45.0°

• 67.5°

Line segment ON is perpendicular to line segment ML, and PN = 10. What is the area of triangle MOL?

• 200 square units

• 250 square units

• 300 square units

• 500 square units