Math Problem Statement

Write the complex number in the form a + bi.

8(cos 30° + i sin 30°)

Solution

The given complex number is in polar form z=r(cosθ+isinθ)z = r (\cos \theta + i \sin \theta). To convert it into the standard rectangular form a+bia + bi, follow these steps:

Given:

  • r=8r = 8
  • θ=30\theta = 30^\circ

Step 1: Use the trigonometric values of cos30\cos 30^\circ and sin30\sin 30^\circ

  • cos30=32\cos 30^\circ = \frac{\sqrt{3}}{2}
  • sin30=12\sin 30^\circ = \frac{1}{2}

Step 2: Expand using r(cosθ+isinθ)r \cdot (\cos \theta + i \sin \theta)

z=8(cos30+isin30)z = 8 \cdot \left( \cos 30^\circ + i \sin 30^\circ \right) z=832+8i12z = 8 \cdot \frac{\sqrt{3}}{2} + 8 \cdot i \cdot \frac{1}{2}

Step 3: Simplify the terms

z=43+4iz = 4\sqrt{3} + 4i

Final Answer:

z=43+4iz = 4\sqrt{3} + 4i

Would you like me to explain any part of the process or provide further examples?


Related Questions:

  1. How do you convert a complex number from rectangular form to polar form?
  2. What are the trigonometric values for other common angles, such as 4545^\circ and 6060^\circ?
  3. How is the magnitude of a complex number calculated?
  4. What are the applications of polar form in electrical engineering or physics?
  5. How do you compute powers of complex numbers in polar form?

Tip:

When working with polar forms, memorize the basic trigonometric values for angles like 30,45,30^\circ, 45^\circ, and 6060^\circ. It simplifies many calculations!

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Math Problem Analysis

Mathematical Concepts

Complex Numbers
Polar and Rectangular Form Conversion
Trigonometry

Formulas

Polar to Rectangular Form: z = r(cos θ + i sin θ) → z = a + bi
Trigonometric Values: cos 30° = √3/2, sin 30° = 1/2

Theorems

Euler's Formula
Trigonometric Properties of Angles

Suitable Grade Level

Grades 10-12