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6.3E: Excersises

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Polar Coordinates

Exercise 6.3E.1

In the following exercises, plot the point whose polar coordinates are given by first constructing the angle θ and then marking off the distance r along the ray.

1) (3,π6)

2) (2,5π3)

3) (0,7π6)

4) (4,3π4)

5) (1,π4)

6) (2,5π6)

7) (1,π2)

Answer

Solution 1:

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Solution 3:

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Solution 5:

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Solution 7:

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Exercise 6.3E.2

For the following exercises, consider the polar graph below. Give two sets of polar coordinates for each point.

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8) Coordinates of point A.

9) Coordinates of point B.

10) Coordinates of point C.

11) Coordinates of point D.

Answer

Solution 9: B(3,π3)B(3,2π3),

Solution 11: D(5,7π6)D(5,π6)

Exercise 6.3E.3

For the following exercises, the rectangular coordinates of a point are given. Find two sets of polar coordinates for the point in (0,2π]. Round to three decimal places.

12) (2,2)

13) (3,4)(3,4)

14) (8,15)

15) (6,8)

16) (4,3)

17) (3,3)

Answer

Solution 13: (5,0.927)(5,0.927+π),

Solution 15: (10,0.927)(10,0.927+π),

Solution 17: 23,0.524)(23,0.524+π)

Exercise 6.3E.4

For the following exercises, find rectangular coordinates for the given point in polar coordinates.

18) (2,5π4)

19) (2,π6)

20) (5,π3)

21) (1,7π6)

22) (3,3π4)

23) (0,π2)

24) (4.5,6.5)

Answer

Solution 19: 3,1),

Solution 21: (32,12),

Solution 23: (0,0)

Exercise 6.3E.5

For the following exercises, determine whether the graphs of the polar equation are symmetric with respect to the x-axis, the y -axis, or the origin.

25) r=3sin(2θ)

26) r2=9cosθ

27) r=cos(θ5)

28) r=2secθ

29) r=1+cosθ

Answer

Solution 25: Symmetry with respect to the x-axis, y-axis, and origin,

Solution 27: Symmetric with respect to x-axis only,

Solution 29: Symmetry with respect to x-axis only.

Exercise 6.3E.6

For the following exercises, describe the graph of each polar equation. Confirm each description by converting into a rectangular equation.

30) r=3

31) θ=π4

32) r=secθ

33) r=cscθ

Answer

Solution 31: Line y=x,

Solution 33: y=1

Exercise 6.3E.7

For the following exercises, convert the rectangular equation to polar form and sketch its graph.

34) x2+y2=16

35) x2y2=16

36) x=8

Answer

Solution 35: Hyperbola; polar form r2cos(2θ)=16 or r2=16secθ.

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Exercise 6.3E.8

For the following exercises, convert the rectangular equation to polar form and sketch its graph.

37) 3xy=2

38) y2=4x

Answer

Solution 37: r=23cosθsinθ

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Exercise 6.3E.9

For the following exercises, convert the polar equation to rectangular form and sketch its graph.

39) r=4sinθ

40) x2+y2=4y

41) r=6cosθ

42) r=θ

43) r=cotθcscθ

Answer

Solution 39:

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Solution 41: xtanx2+y2=y

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Exercise 6.3E.10

For the following exercises, sketch a graph of the polar equation and identify any symmetry.

44) r=1+sinθ

45) r=32cosθ

46) r=22sinθ

47) r=54sinθ

48) r=3cos(2θ)

49) r=3sin(2θ)

50) r=2cos(3θ)

51) r=3cos(θ2)

52) r2=4cos(2θ)

53) r2=4sinθ

54) r=2θ

Answer

Solution 44: y-axis symmetry

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Solution 46: y-axis symmetry

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Solution 48: x- and y-axis symmetry and symmetry about the pole

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Solution 50: x-axis symmetry

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Solution 52: x- and y-axis symmetry and symmetry about the pole

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Solution 54: no symmetry

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Exercise 6.3E.11

55) [T] The graph of r=2cos(2θ)sec(θ). is called a strophoid. Use a graphing utility to sketch the graph, and, from the graph, determine the asymptote.

56) [T] Use a graphing utility and sketch the graph of r=62sinθ3cosθ.

57) [T] Use a graphing utility to graph r=11cosθ.

58) [T] Use technology to graph r=esin(θ)2cos(4θ).

59) [T] Use technology to plot r=sin(3θ7) (use the interval 0θ14π).

60) Without using technology, sketch the polar curve θ=2π3.

61) [T] Use a graphing utility to plot r=θsinθ for πθπ.

62) [T] Use technology to plot r=e0.1θ for 10θ10.

63) [T] There is a curve known as the “Black Hole.” Use technology to plot r=e0.01θ for 100θ100.

64) [T] Use the results of the preceding two problems to explore the graphs of r=e0.001θ and r=e0.0001θ for |θ|>100.

Answer

Solution 56: a line

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Solution 58:

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Solution 60:

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Solution 62:

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Solution 64: Answers vary. One possibility is the spiral lines become closer together and the total number of spirals increases.


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