Mathematics Dictionary
Dr. K. G. Shih
Five point method
Symbol Defintion
Example : Sqr(x) = square root of x
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
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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
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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
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