Math Problem Statement

z^3=8 solve

Solution

To solve the equation z3=8z^3 = 8, we can rewrite it as:

z3=8z^3 = 8

The cube root of 8 is 2, since:

23=82^3 = 8

Thus, one solution is z=2z = 2.

However, since we are dealing with a cubic equation, there can be more solutions in the complex plane. To find all solutions, we express 8 in polar form. The number 8 can be written as:

8=8(cos0+isin0)8 = 8 (\cos 0^\circ + i \sin 0^\circ)

Using De Moivre's Theorem, the general solution for z3=8z^3 = 8 is:

z=2[cos(0+360k3)+isin(0+360k3)]z = 2 \left[ \cos \left( \frac{0^\circ + 360^\circ k}{3} \right) + i \sin \left( \frac{0^\circ + 360^\circ k}{3} \right) \right] where k=0,1,2k = 0, 1, 2.

Now, let's calculate each solution:

  1. For k=0k = 0: z0=2[cos0+isin0]=2z_0 = 2 \left[ \cos 0^\circ + i \sin 0^\circ \right] = 2

  2. For k=1k = 1: z1=2[cos120+isin120]=2(12+i32)=1+i3z_1 = 2 \left[ \cos 120^\circ + i \sin 120^\circ \right] = 2 \left( -\frac{1}{2} + i \frac{\sqrt{3}}{2} \right) = -1 + i\sqrt{3}

  3. For k=2k = 2: z2=2[cos240+isin240]=2(12i32)=1i3z_2 = 2 \left[ \cos 240^\circ + i \sin 240^\circ \right] = 2 \left( -\frac{1}{2} - i \frac{\sqrt{3}}{2} \right) = -1 - i\sqrt{3}

Thus, the three solutions to the equation z3=8z^3 = 8 are:

z0=2,z1=1+i3,z2=1i3z_0 = 2, \quad z_1 = -1 + i\sqrt{3}, \quad z_2 = -1 - i\sqrt{3}

Would you like a more detailed explanation of De Moivre's Theorem or the complex number approach?

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Algebra
Cubic Equations
Complex Numbers
Polar Form
De Moivre's Theorem

Formulas

z^3 = 8
De Moivre's Theorem: z = r[cos(θ + 360k/n) + i sin(θ + 360k/n)]

Theorems

De Moivre's Theorem

Suitable Grade Level

Grades 11-12