1. Circles in the Coordinate Plane
GEOMETRY LESSON 11-5
Pages Exercises
1. (x – 2)2 + (y + 8)2 = 81
2. x2 + (y – 3)2 = 49
3. (x – 0.2)2 + (y – 1.1)2 = 0.16
4. (x – 5)2 + (y + 1)2 = 144
5. (x + 6)2 + (y – 3)2 = 64
6. (x + 9)2 + (y + 4)2 = 5
7. x2 + y2 = 16
8. (x + 4)2 + y2 = 9
9. (x + 1)2 + (y + 1)2 = 1
10. (x + 2)2 + (y – 6)2 = 16
11. (x – 1)2 + (y – 2)2 = 17
12. (x – 7)2 + (y + 2)2 = 52
13. (x + 10)2 + (y + 5)2 = 125
14. (x – 6)2 + (y – 5)2 = 61
15. (x + 1)2 + (y + 4)2 = 25
16. Center: (–7, 5); radius: 4
17. center: (3, –8); radius: 10
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2. Circles in the Coordinate Plane
GEOMETRY LESSON 11-5
18. center: (–4, 1); radius: 5
19. center: (0, 0); radius: 6
20. center: (0.3, 0); radius: 0.2
21. center: (–5, –2);
radius:
22. (x + 4)2 + (y – 2)2 = 16
23. (x – 4)2 + (y + 4)2 = 4
24. (x + 3)2 + (y – 2)2 = 25
25. position: (5, 7); range: 9 units
26. position: (–4, 9); range: 12 units
27. x2 + y2 = 4
28. x2 + y2 = 9
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3. Circles in the Coordinate Plane
GEOMETRY LESSON 11-5
29. x2 + (y – 3)2 = 4
30. (x – 2)2 + y2 = 9
31. (x – 2)2 + (y – 2)2 = 16
32. (x + 1)2 + (y – 1)2 = 4
33. (x – 4)2 + (y – 3)2 = 25
34. (x – 5)2 + (y – 3)2 = 13
35. (x – 3)2 + (y – 3)2 = 8
36. (x + 3)2 + (y + 1.5)2 = 6.25
37. (x + 1.5)2 + (y – 5)2 = 18.25
38. (x – 2)2 + (y + 2)2 = 41
39. x2 + y2 = 1
40. The graph is the point (0, 0).
41. Check students’ work.
42. yes
43. No; the x and y terms are not squared.
44. No; the x term is not squared.
45. circumference: ; area: 64
46. (x – 4)2 + (y – 7)2 = 36
47. x-int. = 13, y-int. =
48. (x – h)2 + (y – k)2 = r2
(y – k)2 = r2 – (x – h)2
y – k = ± r2 – (x – h)2
y = ± r2 – (x – h)2 + k 39 4
11-5

4. Circles in the Coordinate Plane
GEOMETRY LESSON 11-5
49.
50.
51.
52.
53. (3, 2); (2, 3)
54. (4, –1); (–4, 1)
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5. Circles in the Coordinate Plane
GEOMETRY LESSON 11-5
55. (2, 2); (–2, 2)
56. (2, 4)
57. (–4, 4)
58. (3, 5)
59–60. Explanations may vary. Sample: Solve the circle and line eqs. for y, enter in the calc., and use the zooming feature.
61. Answers may vary. Sample: Lines can appear tangent on a graph, but may not be.
62. about 11.5, 11.5, 49.8, 49.8
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6. Circles in the Coordinate Plane
GEOMETRY LESSON 11-5
63. a. x2 + y2 = 15,681,600
b mi
c. 1.2 mi
d. about 32 days
64. a
b. (x + 1)2 + (y – 3)2 + (z – 2)2 = 6
65. D
66. I
67. C
68. [2] This equation is in the standard form of an equation of a circle. This means that r2 = Taking the sq. root of each side, r = 5. Thus, the radius is 5.
[1] incorrect answer OR incorrect explanation
69. [4] The slope of the radius through (6, 3) is , so the
line containing this radius is y = x – . Since
y = 0, x = 2, and the center is (2, 0).
r = (2 – 6)2 + (0 – 3)2 = 5. (x – 2)2 + y2 = 25
[3] appropriate methods, but with one computational error
[2] incorrect equation OR correct equation found incorrectly
[1] correct equation, without work shown 3 4 3 4 3 2
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7. Circles in the Coordinate Plane
GEOMETRY LESSON 11-5
70. x = 25; y = 75
71. 38
72. 6, 12
73. –5, 2
74. 4, 4
75. 11, –7
76. 6
79. 3
81. 3 4
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