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Given z = (5)/(2-i) - (3+2i), find z2 and its modulus and argument. Then, solve the equation (z)/(1+2i) + (z-1)/(5) = (1)/(1-2i) for z.

Mathematics

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Answers

2 parts
i

-1-i

2

π2\frac{\pi}{2}

ii
4
-3

Step-by-step solution

14 steps

Here's the solution for question 5:

Part i· 5 steps

Given z=52−i−(3+2i)z = \frac{5}{2-i} - (3+2i).

  1. Express the first term in the form a+bia+bi.

    52−i=52−i×2+i2+i=5(2+i)22−i2=10+5i4−(−1)=10+5i5=2+i\frac{5}{2-i} = \frac{5}{2-i} \times \frac{2+i}{2+i} = \frac{5(2+i)}{2^2 - i^2} = \frac{10+5i}{4 - (-1)} = \frac{10+5i}{5} = 2+i
  2. Substitute this back into the expression for zz and simplify.

    z=(2+i)−(3+2i)=2+i−3−2i=(2−3)+(1−2)i=−1−iz = (2+i) - (3+2i) = 2+i-3-2i = (2-3) + (1-2)i = -1-i

    So, zz in the form x+iyx+iy is −1−i\boxed{-1-i}.

  3. Calculate z2z^2.

    z2=(−1−i)2=(−(1+i))2=(1+i)2=12+2(1)(i)+i2=1+2i−1=2iz^2 = (-1-i)^2 = (-(1+i))^2 = (1+i)^2 = 1^2 + 2(1)(i) + i^2 = 1+2i-1 = 2i
  4. Find ∣z2∣|z^2|.

    For z2=0+2iz^2 = 0+2i, the modulus is:

    ∣z2∣=02+22=4=2|z^2| = \sqrt{0^2 + 2^2} = \sqrt{4} = 2

    So, ∣z2∣=2|z^2| = \boxed{2}.

  5. Find arg⁡z2\arg z^2.

    For z2=2iz^2 = 2i, the complex number lies on the positive imaginary axis.

    arg⁡z2=π2\arg z^2 = \frac{\pi}{2}

    So, arg⁡z2=π2\arg z^2 = \boxed{\frac{\pi}{2}}.

Part ii4

Given that z1+2i+z−15=11−2i\frac{z}{1+2i} + \frac{z-1}{5} = \frac{1}{1-2i}.

  1. Simplify the terms involving complex denominators.

    z1+2i=z(1−2i)(1+2i)(1−2i)=z(1−2i)12−(2i)2=z(1−2i)1+4=z(1−2i)5\frac{z}{1+2i} = \frac{z(1-2i)}{(1+2i)(1-2i)} = \frac{z(1-2i)}{1^2 - (2i)^2} = \frac{z(1-2i)}{1+4} = \frac{z(1-2i)}{5} 11−2i=1(1+2i)(1−2i)(1+2i)=1+2i12−(2i)2=1+2i1+4=1+2i5\frac{1}{1-2i} = \frac{1(1+2i)}{(1-2i)(1+2i)} = \frac{1+2i}{1^2 - (2i)^2} = \frac{1+2i}{1+4} = \frac{1+2i}{5}
  2. Substitute these simplified terms back into the equation.

    z(1−2i)5+z−15=1+2i5\frac{z(1-2i)}{5} + \frac{z-1}{5} = \frac{1+2i}{5}
  3. Multiply the entire equation by 5 to clear the denominators.

    z(1−2i)+(z−1)=1+2iz(1-2i) + (z-1) = 1+2i z−2iz+z−1=1+2iz - 2iz + z - 1 = 1+2i 2z−2iz−1=1+2i2z - 2iz - 1 = 1+2i z(2−2i)=1+2i+1z(2-2i) = 1+2i+1 z(2−2i)=2+2iz(2-2i) = 2+2i
  4. Solve for zz.

    z=2+2i2−2i=2(1+i)2(1−i)=1+i1−iz = \frac{2+2i}{2-2i} = \frac{2(1+i)}{2(1-i)} = \frac{1+i}{1-i}

    Multiply by the conjugate of the denominator:

    z=1+i1−i×1+i1+i=(1+i)212−i2=1+2i+i21−(−1)=1+2i−12=2i2=iz = \frac{1+i}{1-i} \times \frac{1+i}{1+i} = \frac{(1+i)^2}{1^2 - i^2} = \frac{1+2i+i^2}{1 - (-1)} = \frac{1+2i-1}{2} = \frac{2i}{2} = i

    So, z=iz=i.

  5. Find real numbers pp and qq such that (p+iq)z=3+4i(p+iq)z = 3+4i.

    Substitute z=iz=i:

    (p+iq)i=3+4i(p+iq)i = 3+4i pi+i2q=3+4ipi + i^2q = 3+4i pi−q=3+4ipi - q = 3+4i

    Rearrange to group real and imaginary parts:

    −q+pi=3+4i-q + pi = 3+4i

    Equating the real parts:

    −q=3  ⟹  q=−3-q = 3 \implies q = -3

    Equating the imaginary parts:

    p=4p = 4

    So, p=4p = \boxed{4} and q=−3q = \boxed{-3}.

Part iii· 4 steps

Find the general solution of the equation cos⁡2x+1=sin⁡2x\cos 2x + 1 = \sin 2x.

  1. Use the double angle identity cos⁡2x=2cos⁡2x−1\cos 2x = 2\cos^2 x - 1.

    (2cos⁡2x−1)+1=sin⁡2x(2\cos^2 x - 1) + 1 = \sin 2x 2cos⁡2x=sin⁡2x2\cos^2 x = \sin 2x
  2. Use the double angle identity sin⁡2x=2sin⁡xcos⁡x\sin 2x = 2\sin x \cos x.

    2cos⁡2x=2sin⁡xcos⁡x2\cos^2 x = 2\sin x \cos x
  3. Rearrange the equation and factor.

    2cos⁡2x−2sin⁡xcos⁡x=02\cos^2 x - 2\sin x \cos x = 0 2cos⁡x(cos⁡x−sin⁡x)=02\cos x (\cos x - \sin x) = 0
  4. Solve for the two possible cases.

    Case 1: 2cos⁡x=02\cos x = 0

    cos⁡x=0\cos x = 0

    The general solution for cos⁡x=0\cos x = 0 is x=π2+nπx = \frac{\pi}{2} + n\pi, where n∈Zn \in \mathbb{Z}.

    Case 2: cos⁡x−sin⁡x=0\cos x - \sin x = 0

    cos⁡x=sin⁡x\cos x = \sin x

    Divide by cos⁡x\cos x (assuming $\cos x \neq

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