Problem Set 68: Rotation of Axes

1. What effect does the xyxy term have on the graph of a conic section?

2. If the equation of a conic section is written in the form Ax2+By2+Cx+Dy+E=0Ax2+By2+Cx+Dy+E=0 and AB=0AB=0, what can we conclude?

3. If the equation of a conic section is written in the form Ax2+Bxy+Cy2+Dx+Ey+F=0Ax2+Bxy+Cy2+Dx+Ey+F=0, and B24AC>0B24AC>0, what can we conclude?

4. Given the equation ax2+4x+3y212=0ax2+4x+3y212=0, what can we conclude if a>0?a>0?

5. For the equation Ax2+Bxy+Cy2+Dx+Ey+F=0Ax2+Bxy+Cy2+Dx+Ey+F=0, the value of θθ that satisfies cot(2θ)=ACBcot(2θ)=ACB gives us what information?

For the following exercises, determine which conic section is represented based on the given equation.

6. 9x2+4y2+72x+36y500=09x2+4y2+72x+36y500=0

7. x210x+4y10=0x210x+4y10=0

8. 2x22y2+4x6y2=02x22y2+4x6y2=0

9. 4x2y2+8x1=04x2y2+8x1=0

10. 4y25x+9y+1=04y25x+9y+1=0

11. 2x2+3y28x12y+2=02x2+3y28x12y+2=0

12. 4x2+9xy+4y236y125=04x2+9xy+4y236y125=0

13. 3x2+6xy+3y236y125=03x2+6xy+3y236y125=0

14. 3x2+33xy4y2+9=03x2+33xy4y2+9=0

15. 2x2+43xy+6y26x3=02x2+43xy+6y26x3=0

16. x2+42xy+2y22y+1=0x2+42xy+2y22y+1=0

17. 8x2+42xy+4y210x+1=0

For the following exercises, find a new representation of the given equation after rotating through the given angle.

18. 3x2+xy+3y25=0,θ=45

19. 4x2xy+4y22=0,θ=45

20. 2x2+8xy1=0,θ=30

21. 2x2+8xy+1=0,θ=45

22. 4x2+2xy+4y2+y+2=0,θ=45

For the following exercises, determine the angle θ that will eliminate the xy term and write the corresponding equation without the xy term.

23. x2+33xy+4y2+y2=0

24. 4x2+23xy+6y2+y2=0

25. 9x233xy+6y2+4y3=0

26. 3x23xy2y2x=0

27. 16x2+24xy+9y2+6x6y+2=0

28. x2+4xy+4y2+3x2=0

29. x2+4xy+y22x+1=0

30. 4x223xy+6y21=0

For the following exercises, rotate through the given angle based on the given equation. Give the new equation and graph the original and rotated equation.

31. y=x2,θ=45

32. x=y2,θ=45

33. x24+y21=1,θ=45

34. y216+x29=1,θ=45

35. y2x2=1,θ=45

36. y=x22,θ=30

37. x=(y1)2,θ=30

38. x29+y24=1,θ=30

For the following exercises, graph the equation relative to the xy system in which the equation has no xy term.

39. xy=9

40. x2+10xy+y26=0

41. x210xy+y224=0

42. 4x233xy+y222=0

43. 6x2+23xy+4y221=0

44. 11x2+103xy+y264=0

45. 21x2+23xy+19y218=0

46. 16x2+24xy+9y2130x+90y=0

47. 16x2+24xy+9y260x+80y=0

48. 13x263xy+7y216=0

49. 4x24xy+y285x165y=0

For the following exercises, determine the angle of rotation in order to eliminate the xy term. Then graph the new set of axes.

50. 6x253xy+y2+10x12y=0

51. 6x25xy+6y2+20xy=0

52. 6x283xy+14y2+10x3y=0

53. 4x2+63xy+10y2+20x40y=0

54. 8x2+3xy+4y2+2x4=0

55. 16x2+24xy+9y2+20x44y=0

For the following exercises, determine the value of k based on the given equation.

56. Given 4x2+kxy+16y2+8x+24y48=0, find k for the graph to be a parabola.

57. Given 2x2+kxy+12y2+10x16y+28=0, find k for the graph to be an ellipse.

58. Given 3x2+kxy+4y26x+20y+128=0, find k for the graph to be a hyperbola.

59. Given kx2+8xy+8y212x+16y+18=0, find k for the graph to be a parabola.

60. Given 6x2+12xy+ky2+16x+10y+4=0, find k for the graph to be an ellipse.