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Mathematics Dictionary
Dr. K. G. Shih

Five point method


  • Q01 | - Diagram : Sine curve y = sin(x)
  • Q02 | - Sketch y = sin(x) using five point method
  • Q03 | - Sketch y = 2*sin(2*x) using five point method
  • Q04 | - Sketch y = Sqr(3)*cos(x) + sin(x) using five point method

  • Q01. Sine Curve : y = sin(x)




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    Q02. Sketch y = sin(x) using five points

    Solution
    • The period of sine finction is 2*pi
    • Hence we can sketch the function from 0 to 2*pi
    • Five points

      • x ...... 0 ...... pi/2 ..... pi ...... 1.5*pi ...... 2*pi
      • y ...... 0 ...... 1 ........ 0 ....... -1 .......... 0

    • Five points (0, 0), (pi/2 ,1), (pi, 0), (1.5*pi, -1), (2*pi, 0)
    • Since we know this is sine curve
    • Hence we can use these five points to sketch the sine curve

    Go to Begin

    Q03. Sketch y = 2*sin(2*x) using five points method

    Solution
    • The period of sine finction is 2*x = 2*pi = pi
    • Hence we can sketch the function from 0 to pi
    • Five points : let t = 2*x

      • t ...... 0 ...... pi/2 ..... pi ........ 1.5*pi ....... 2*pi
      • x ...... 0 ...... pi/4 ..... pi/2 ...... 0.75*pi ...... 1*pi
      • y ...... 0 ...... 2 ........ 0 ......... -2 ........... 0

    • Five points (0, 0), (pi/4 ,2), (pi/2, 0), (0.75*pi, -2), (pi, 0)
    • Since we know this is sine curve
    • Hence we can use these five points to sketch the sine curve from x = 0 to pi

    Go to Begin

    Q4. Sketch y = Sqr(3)*cos(x) + sin(x) using five point method

    Solution
    • Since sin(60) = Sqr(3)/2 ans cos(x) = 1/2
    • Hence y = 2*sin(60)*cos(x) + sin(x)*cos(60)
    • Hence y = 2*sin(x + pi/3)
    • The period of sine finction is 2*pi
    • Hence we can sketch the function from 0 to pi
    • Five points : let t = x + pi/3

      • t ...... 0 ........ pi/2 ..... pi ......... 1.5*pi ...... 2*pi
      • x ...... -pi/3..... pi/6 ..... 2*pi/3 ..... 7*pi/6 ...... 1*pi
      • y ...... 0 ........ 2 ........ 0 .......... -2 .......... 0

    • Five points (0, 0), (pi/6 ,2), (2*pi/3, 0), (7*pi/6, -2), (5*pi/3, 0)
    • Since we know this is sine curve
    • Hence we can use these five points to sketch the sine curve from x = 0 to pi

    Go to Begin

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    Copyright © Dr. K. G. Shih, Nova Scotia, Canada.

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