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Learn circle vocabulary, chord, diameter, equations, and intersecting circles with clear examples and solutions. Improve your circle knowledge now!
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Concept 52 Circles and their parts
Vocabulary • Circle – the set of all points equidistant from a center.
A. B. C. D. 3. Name the circle and identify a radius.
A. B. C. D. 4. Which segment is not a chord?
5. If RT = 21 cm, what is the length of QV? RT is a diameter and QV is a radius. d = 2r Diameter Formula 21 = 2rd = 21 10.5 = r Simplify. Answer:QV = 10.5 cm
6. If QS = 26 cm, what is the length of RV? A. 12 cm B. 13 cm C. 16 cm D. 26 cm
Find Measures in Intersecting Circles 7. First, find ZY. WZ + ZY = WY 5 + ZY = 8 ZY = 3 Next, find XY. XZ + ZY = XY 11 + 3 = XY 14 = XY
8. A. 3 in. B. 5 in. C. 7 in. D. 9 in.
Equations of Circles Concept 53
1. Write the equation of the circle with a center at (3, –3) and a radius of 6. (x – h)2 + (y – k)2 = r2 Equation of circle (x – 3)2 + (y – (–3))2 = 62 Substitution (x – 3)2 + (y + 3)2 = 36 Simplify. Answer:(x – 3)2 + (y + 3)2 = 36
2. Write the equation of the circle graphed to the right. The center is at (1, 3) and the radius is 2. (x – h)2 + (y – k)2 = r2 Equation of circle (x – 1)2 + (y – 3)2 = 22 Substitution (x – 1)2 + (y – 3)2 = 4 Simplify. Answer:(x – 1)2 + (y – 3)2 = 4
3. Write the equation of the circle with a center at (2, –4) and a radius of 4. A.(x – 2)2 + (y + 4)2 = 4 B.(x + 2)2 + (y – 4)2 = 4 C.(x – 2)2 + (y + 4)2 = 16 D.(x + 2)2 + (y – 4)2 = 16
4. Write the equation of the circle graphed to the right. A.x2 + (y + 3)2 = 3 B.x2 + (y – 3)2 = 3 C.x2 + (y + 3)2 = 9 D.x2 + (y – 3)2 = 9
x2 + (y + 3)2 = 9 5. List the center and radius length of the circle with the formula x2 + (y + 3)2 = 9. (x – 0) 2 + (y – -3)2 = (3) 2 (0, -3) R = 3
6. List the center and radius length of the circle with the formula (x + 3)2 + (y – 2)2 = 18 (x – -3)2 + (y – 2)2 = 18
7. Write the equation of the circle that has its center at (–3, –2) and passes through (1, –2). (x – h)2 + (y – k)2 = r2 (x + 3)2 + (y + 2)2 = r2 Plug it in (1 + 3)2 + (-2 + 2)2 = r2 (4)2 + (0)2 = r2 16 = r2 Answer:(x + 3)2 + (y + 2)2 = 16
8. Write the equation of the circle that has its center at (–1, 0) and passes through (3, 0). (x – h)2 + (y – k)2 = r2 (x + 1)2 + (y + 0)2 = r2 Plug it in (3 + 1)2 + (0 + 0)2 = r2 (4)2 + (0)2 = r2 16 = r2 Answer:(x + 1)2 + y2 = 16