Complex Numbers Flashcards

(21 cards)

1
Q

Draw argand and show z* and iz

A

z* - 90˚ right
iz - 90˚ left

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2
Q

Show different forms of z: de moivre, with e

A

(cosθ + i sin θ)
re^iθ

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3
Q

Show roots of r^n = 1 and formula for the angles

A

distributed around a circle at angles 2π/n

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4
Q

(z)(z*)

A

|z|^2

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5
Q

z1^z2

A

e^(z2 ln z1)

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6
Q

z + z*

A

2 re(z)

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7
Q

z - z*

A

2 im(z)

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8
Q

|1/z|

A

1/r

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9
Q

arg(1/z)

A

-arg(z)

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10
Q

State cos n𝜃 and sin n𝜃

A

Re(cos + isin)^n
Im(cos + isin)^n

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11
Q

State cos 𝜃 and sin 𝜃 in terms of e and i

A

1/2 (e^i𝜃 + e^-i𝜃)
1/2i (e^i𝜃 - e^-i𝜃)

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12
Q

cos^n 𝜃 and sin^n 𝜃

A

[1/2 (e^i𝜃 + e^-i𝜃)]^n
[1/2i (e^i𝜃 - e^-i𝜃)]^n

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13
Q

SN = ∑k=0N-1 cos k 𝜃

A

Re[a (1-e^iN𝜃 / 1 - e^i𝜃)]

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14
Q

SN = 0∑N-1 sin k 𝜃

A

Im[a (1-e^iN𝜃 / 1 - e^i𝜃)]

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15
Q

SN = 1∑N-1 cos k 𝜃

A

Re[a e^ik𝜃 (1-e^iN𝜃 / 1 - e^i𝜃)]

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16
Q

SN = 1∑N-1 sin k 𝜃

A

Im[a e^ik𝜃 (1-e^iN𝜃 / 1 - e^i𝜃)]

17
Q

Evaluate ln z

A

z = 2^i = cos ln 2 + i sin ln 2

18
Q

Find roots of z^n = a

A

e^inθ = e^ix
θ = (x+2πk)/n, 0≤ k ≤ n-1

19
Q

Give oscillation equation and define each part

A

x(t) = a cos wt + b sin wt = Re[A e^iwt]
A = a - ib

20
Q

Give velocity, amplitude, phase

A

v(t) = dx/dt = Re[iwA e^iwt]
Amplitude = |A|
phase = θ

21
Q

State fundamental theory of algebra

A

P(z) fo degree n has n complex roots