Mathematics Dictionary
Dr. K. G. Shih
Power 5 Equation or quaint equation
Questions
Read Symbol defintion
Q01 |
- Solve x^5 + 1 = 0
Q02 |
- Solve x^5 - 1 = 0
Q03 |
- Solve x^5 + i = 0
Q04 |
- Solve x^5 - i = 0
Q05 |
- Show that 0.30901 + 0.95106*i is a root of x^5 - 1 = 0
Q06 |
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Q07 |
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Q08 |
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Q09 |
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Q10 |
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Answers
Q01. Solve x^5 + 1 = 0
De Moivre's Theory : Draw a unit circle
1. Draw 1st point on circle with angle : A1 = 036
2. Draw 2nd point on circle with angle : A2 = 108
3. Draw 3nd point on circle with angle : A3 = 180
4. Draw 4nd point on circle with angle : A3 = 252
5. Draw 5nd point on circle with angle : A3 = 324
Solutions : Use calculator
r1 = cos(A1) + i*sin(A1)
r2 = cos(A2) + i*sin(A2)
r3 = cos(A3) + i*sin(A3)
r4 = cos(A4) + i*sin(A4)
r5 = cos(A5) + i*sin(A5)
Solutions : By constuctions
For angle A1 : r1 = x1 + i*y1. Measure x1 and y1
For angle A2 : r2 = x2 + i*y2. Measure x2 and y2
Similarly find other five solutions
Use the conjugate complex to reduce the calculation
Go to Begin
Q02. Solve x^5 - 1 = 0
De Moivre's Theory : Draw a unit circle
1. Draw 1st point on circle with angle : A1 = 000
2. Draw 2nd point on circle with angle : A2 = 072
3. Draw 3nd point on circle with angle : A3 = 144
4. Draw 4nd point on circle with angle : A3 = 216
5. Draw 5nd point on circle with angle : A3 = 288
Solutions : Use calculator
r1 = cos(A1) + i*sin(A1)
r2 = cos(A2) + i*sin(A2)
r3 = cos(A3) + i*sin(A3)
r4 = cos(A4) + i*sin(A4)
r5 = cos(A5) + i*sin(A5)
Solutions : By constuctions
For angle A1 : r1 = x1 + i*y1. Measure x1 and y1
For angle A2 : r2 = x2 + i*y2. Measure x2 and y2
Similarly find other five solutions
Use the conjugate complex to reduce the calculation
Go to Begin
Q03. Solve x^5 + i = 0
De Moivre's Theory : Draw a unit circle
1. Draw 1st point on circle with angle : A1 = 054
2. Draw 2nd point on circle with angle : A2 = 126
3. Draw 3nd point on circle with angle : A3 = 198
4. Draw 4nd point on circle with angle : A3 = 270
5. Draw 5nd point on circle with angle : A3 = 342
Solutions : Use calculator
r1 = cos(A1) + i*sin(A1)
r2 = cos(A2) + i*sin(A2)
r3 = cos(A3) + i*sin(A3)
r4 = cos(A4) + i*sin(A4)
r5 = cos(A5) + i*sin(A5)
Solutions : By constuctions
For angle A1 : r1 = x1 + i*y1. Measure x1 and y1
For angle A2 : r2 = x2 + i*y2. Measure x2 and y2
Similarly find other five solutions
Go to Begin
Q04. x^5 - i = 0
De Moivre's Theory : Draw a unit circle
1. Draw 1st point on circle with angle : A1 = 018
2. Draw 2nd point on circle with angle : A2 = 090
3. Draw 3nd point on circle with angle : A3 = 162
4. Draw 4nd point on circle with angle : A3 = 234
5. Draw 5nd point on circle with angle : A3 = 306
Solutions : Use calculator
r1 = cos(A1) + i*sin(A1)
r2 = cos(A2) + i*sin(A2)
r3 = cos(A3) + i*sin(A3)
r4 = cos(A4) + i*sin(A4)
r5 = cos(A5) + i*sin(A5)
Solutions : By constuctions
For angle A1 : r1 = x1 + i*y1. Measure x1 and y1
For angle A2 : r2 = x2 + i*y2. Measure x2 and y2
Similarly find other five solutions
Go to Begin
Q05. Show that 0.30901 + 0.95106*i is a root of x^5 - 1 = 0
Proof
x^5 - 1 = (0.30901 + 0.95106*i)^5 - 1
= (0.30901)^5
+ 05*((0.30901)^4)*((0.95106)^1)*i
+ 10*((0.30901)^3)*((0.95106)^2)*(i^2)
+ 10*((0.30901)^2)*((0.95106)^3)*(i^3)
+ 05*((0.30901)^1)*((0.95106)^4)*(i^4)
+ 01**((0.95106)^5)*(i^5)
- 1
= 0.002817 + 5*0.0091178*0.95106*i + 10*0.0295064*0.904515*(-1)
+ 10*0.09548718*0.860248*(-i) + 5*0.30901*0.8181476*(+1) + 0.778107*(i) - 1
= 0.02817 + 0.0433578*i - 0.2668898 - 0.821426556*i + 1.2640789 + 0.778107*i - 1
= 0.0000 + 0.0000*i
Go to Begin
Q06.
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Q07.
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Q08.
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Q09. Answer
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Q10. Answer
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