Let [tex] z = 38\left(\cos \left(\frac{\pi}{8}\right) + i \sin \left(\frac{\pi}{8}\right)\right) [/tex] and [tex] w = 2\left(\cos \left(\frac{\pi}{16}\right) + i \sin \left(\frac{\pi}{16}\right)\right) [/tex].

What is the product of [tex] zw [/tex]?

A. [tex] 40\left(\cos \left(\frac{\pi}{16}\right) + i \sin \left(\frac{\pi}{16}\right)\right) [/tex]
B. [tex] 76\left(\cos \left(\frac{\pi}{16}\right) + i \sin \left(\frac{\pi}{16}\right)\right) [/tex]
C. [tex] 40\left(\cos \left(\frac{3\pi}{16}\right) + i \sin \left(\frac{3\pi}{16}\right)\right) [/tex]
D. [tex] 76\left(\cos \left(\frac{3\pi}{16}\right) + i \sin \left(\frac{3\pi}{16}\right)\right) [/tex]



Answer :

To find the product of the complex numbers [tex]\( z \)[/tex] and [tex]\( w \)[/tex], we need to use the properties of complex numbers in polar form.

### Step-by-Step Solution

1. Identify the magnitudes and angles of [tex]\( z \)[/tex] and [tex]\( w \)[/tex]:
- For [tex]\( z \)[/tex]:
- Magnitude: [tex]\( |z| = 38 \)[/tex]
- Angle: [tex]\( \arg(z) = \frac{\pi}{8} \)[/tex]
- For [tex]\( w \)[/tex]:
- Magnitude: [tex]\( |w| = 2 \)[/tex]
- Angle: [tex]\( \arg(w) = \frac{\pi}{16} \)[/tex]

2. Calculate the magnitude of the product [tex]\( zw \)[/tex]:
- The magnitude of the product of two complex numbers is the product of their magnitudes:
[tex]\[ |zw| = |z| \cdot |w| = 38 \cdot 2 = 76 \][/tex]

3. Calculate the angle of the product [tex]\( zw \)[/tex]:
- The angle of the product of two complex numbers is the sum of their angles:
[tex]\[ \arg(zw) = \arg(z) + \arg(w) = \frac{\pi}{8} + \frac{\pi}{16} \][/tex]
- To add these fractions, find a common denominator (which is 16):
[tex]\[ \frac{\pi}{8} = \frac{2\pi}{16} \][/tex]
[tex]\[ \frac{2\pi}{16} + \frac{\pi}{16} = \frac{3\pi}{16} \][/tex]

4. Express [tex]\( zw \)[/tex] in its final form:
[tex]\[ zw = 76 \left( \cos \left( \frac{3\pi}{16} \right) + i \sin \left( \frac{3\pi}{16} \right) \right) \][/tex]

Therefore, the product [tex]\( zw \)[/tex] is:
[tex]\[ 76 \left( \cos \left( \frac{3\pi}{16} \right) + i \sin \left( \frac{3\pi}{16} \right) \right) \][/tex]

Hence, the correct answer is:
[tex]\[ \boxed{76 \left( \cos \left( \frac{3\pi}{16} \right) + i \sin \left( \frac{3\pi}{16} \right) \right)} \][/tex]