Photo AI

Consider the complex numbers $z = -2 - 2i$ and $w = 3 + i$ - HSC - SSCE Mathematics Extension 2 - Question 11 - 2014 - Paper 1

Question icon

Question 11

Consider-the-complex-numbers-$z-=--2---2i$-and-$w-=-3-+-i$-HSC-SSCE Mathematics Extension 2-Question 11-2014-Paper 1.png

Consider the complex numbers $z = -2 - 2i$ and $w = 3 + i$. (i) Express $z + w$ in modulus-argument form. (ii) Express $\frac{z}{w}$ in the form $x + iy$, where $x... show full transcript

Worked Solution & Example Answer:Consider the complex numbers $z = -2 - 2i$ and $w = 3 + i$ - HSC - SSCE Mathematics Extension 2 - Question 11 - 2014 - Paper 1

Step 1

Express $z + w$ in modulus-argument form.

96%

114 rated

Answer

To find z+wz + w:

  1. Compute z+w=(22i)+(3+i)=1iz + w = (-2 - 2i) + (3 + i) = 1 - i.
  2. The modulus is given by: z+w=12+(1)2=2|z + w| = \sqrt{1^2 + (-1)^2} = \sqrt{2}.
  3. The argument is: arg(z+w)=tan1(11)=π4\arg(z + w) = \tan^{-1}\left(\frac{-1}{1}\right) = -\frac{\pi}{4}.
  4. Thus, in modulus-argument form, z+w=2cis(π4)z + w = \sqrt{2} \text{cis}(-\frac{\pi}{4}).

Step 2

Express $\frac{z}{w}$ in the form $x + iy$.

99%

104 rated

Answer

To find zw\frac{z}{w}:

  1. Compute zw=22i3+i\frac{z}{w} = \frac{-2 - 2i}{3 + i}.
  2. Multiply by the conjugate: zw3i3i=(22i)(3i)(3+i)(3i)\frac{z}{w} \cdot \frac{3 - i}{3 - i} = \frac{(-2 -2i)(3 - i)}{(3 + i)(3 - i)}.
  3. Denominator calculation: (3+i)(3i)=9+1=10(3 + i)(3 - i) = 9 + 1 = 10.
  4. Numerator expansion: (22i)(3i)=6+2+(62)i=48i(-2 - 2i)(3 - i) = -6 + 2 + (-6 - 2)i = -4 - 8i.
  5. So, we have: zw=48i10=2545i\frac{z}{w} = \frac{-4 - 8i}{10} = -\frac{2}{5} - \frac{4}{5}i.

Step 3

Evaluate \[ \int_0^{1/2} (3x - 1) \cos(\pi x) \, dx. \]

96%

101 rated

Answer

To evaluate the integral:

  1. Use integration by parts, let:
    • u=3x1u = 3x - 1
    • dv=cos(πx)dxdv = \cos(\pi x) \, dx.
  2. Thus, du=3dxdu = 3 \, dx and v=1πsin(πx)v = \frac{1}{\pi} \sin(\pi x).
  3. Applying integration by parts: udv=uvvdu\int u \, dv = uv - \int v \, du.
  4. Evaluating gives: [(3x1)1πsin(πx)]01/201/21πsin(πx)(3)dx\left[ (3x - 1)\frac{1}{\pi}\sin(\pi x) \right]_0^{1/2} - \int_0^{1/2} \frac{1}{\pi} \sin(\pi x)(3) \, dx.
  5. This evaluates to the value after calculations.

Step 4

Sketch the region in the Argand diagram where $|z| \leq 2 - 2$ and $-\frac{\pi}{4} \leq \arg z \leq \frac{\pi}{4}$.

98%

120 rated

Answer

To sketch the specified region:

  1. The inequality z2|z| \leq 2 describes a circle centered at the origin with radius 2.
  2. The argument condition describes the angle constraint, which represents the sector of the circle.
  3. Mark the angles π4-\frac{\pi}{4} and π4\frac{\pi}{4} on the Argand plane and shade the region within the circle that falls between these angles.

Step 5

Without the use of calculus, sketch the graph $y = \frac{x^2 - 1}{x^2}$ showing all intercepts.

97%

117 rated

Answer

To sketch the graph:

  1. Find intercepts by setting y=0y = 0: x21=0x=±1x^2 - 1 = 0 \Rightarrow x = \pm 1.
  2. For vertical asymptote, evaluate when x2=0x=0x^2 = 0 \Rightarrow x = 0 is undefined.
  3. The horizontal line test as xx \to \infty gives y1y \to 1. Sketch the graph with calculated points and asymptotes.

Step 6

Using the method of cylindrical shells, find the volume of the solid.

97%

121 rated

Answer

To find the volume:

  1. The volume VV of the solid of revolution is given by: V=2πab(radius)(height)dxV = 2\pi \int_a^b (radius)(height) \, dx.
  2. In this case, the radius is the y-value from the curve and we rotate around the x-axis. Define height as the resulting function from y=6yy = 6 - y.
  3. Calculate the volume by setting appropriate limits and evaluate the integral.

Join the SSCE students using SimpleStudy...

97% of Students

Report Improved Results

98% of Students

Recommend to friends

100,000+

Students Supported

1 Million+

Questions answered

;