All flashcards
Flashcard 1: What is z-bar{z} in terms of Im(z)?
Answer: z-bar{z}=2Im(z)i. Difference gives twice the imaginary part times i.
Flashcard 2: What is the geometric meaning of multiplying by −1?
Answer: Rotation by 180^circ about the origin. Multiplication by −1 rotates by half a turn.
Flashcard 3: What is the geometric meaning of multiplying by i?
Answer: Rotation by 90^circ counterclockwise. Multiplication by i rotates by a quarter turn left.
Flashcard 4: What is z+bar{z} in terms of Re(z)?
Answer: z+bar{z}=2Re(z). Sum of conjugates equals twice the real part.
Flashcard 5: What is the geometric meaning of multiplying by a real k>0?
Answer: Dilation by factor k from the origin. Positive real scaling stretches by factor k.
Flashcard 6: What is z2z1ˉ for z2=0?
Answer: z2z1ˉ=z2ˉz1ˉ. Conjugate distributes over division.
Flashcard 7: What is i(4−3i)?
Answer: 3+4i. Distribute i and use i2=−1.
Flashcard 8: What is zbar{z} for z=a+bi?
Answer: zbar{z}=a^2+b^2. Product of a complex number with its conjugate gives modulus squared.
Flashcard 9: What is the geometric meaning of multiplying by −i?
Answer: Rotation by 90^circ clockwise. Multiplication by −i rotates by a quarter turn right.
Flashcard 10: What is the geometric meaning of multiplying by a real k<0?
Answer: Dilation by k and rotation by 180^circ. Negative real scaling stretches and reflects through origin.
Flashcard 11: What happens to arguments under multiplication: arg(z_1z_2)?
Answer: arg(z_1z_2)=arg(z_1)+arg(z_2). Arguments add when complex numbers are multiplied.
Flashcard 12: What is bar{z_1z_2} in terms of bar{z_1} and bar{z_2}?
Answer: bar{z_1z_2}=bar{z_1}bar{z_2}. Conjugate distributes over multiplication.
Flashcard 13: What is bar{(z_1+z_2)} in terms of conjugates?
Answer: bar{(z_1+z_2)}=bar{z_1}+bar{z_2}. Conjugate distributes over addition.
Flashcard 14: What is the result of conjugating twice: bar{(bar{z})}?
Answer: bar{(bar{z})}=z. Double conjugation returns the original number.
Flashcard 15: What is the argument relation between z and bar{z} (for zneq 0)?
Answer: arg(bar{z})=-arg(z). Conjugate has opposite argument from original.
Flashcard 16: What is Re(z) and Im(z) for z=a+bi?
Answer: Re(z)=a,Im(z)=b. Real part is coefficient of 1, imaginary part is coefficient of i.
Flashcard 17: What is the geometric meaning of z1z2 in polar form?
Answer: Multiply moduli; add arguments (scale and rotate). Multiplication scales and rotates simultaneously.
Flashcard 18: What is (5-2i)-(1+7i)?
Answer: 4−9i. Subtract real parts and imaginary parts separately.
Flashcard 19: What happens to arguments under division: arg(z2z1)?
Answer: arg(z2z1)=arg(z1)−arg(z2). Arguments subtract when complex numbers are divided.
Flashcard 20: What is the complex conjugate of z=a+bi?
Answer: zˉ=a−bi. Change the sign of the imaginary part only.
Flashcard 21: What is zzˉ if z=3−4i?
Answer: 25. Apply formula zzˉ=a2+b2.
Flashcard 22: What is the conjugate of −6+11i?
Answer: −6−11i. Negate the imaginary part to find conjugate.
Flashcard 23: What point on the complex plane represents z=a+bi?
Answer: (a,b). Real part is the x-coordinate, imaginary part is the y-coordinate.
Flashcard 24: What complex number corresponds to the point (x,y) on the complex plane?
Answer: x+yi. x-coordinate becomes real part, y-coordinate becomes imaginary part.
Flashcard 25: What is the argument heta of z on the complex plane?
Answer: Angle from positive real axis to z. Measured counterclockwise from positive x-axis.
Flashcard 26: What is Euler form of a complex number z in polar coordinates?
Answer: z=reiheta. Euler's formula: eiθ=cosθ+isinθ.
Flashcard 27: What is the geometric effect of adding complex numbers z1+z2?
Answer: Vector addition (translate head-to-tail). Place vectors end-to-end to find the sum.
Flashcard 28: What is the geometric effect of subtracting z1−z2?
Answer: Add z1+(−z2) (difference of vectors). Subtract by adding the negative vector.
Flashcard 29: What point represents −z if z=a+bi?
Answer: (−a,−b). Negation reflects the point through the origin.
Flashcard 30: What is the geometric effect of conjugation z mapsto bar{z}?
Answer: Reflection across the real axis. Conjugation mirrors the point across the x-axis.