Precalculus Examples

$- 1$

Step 1

This is the trigonometric form of a complex number where $| z |$ is the modulus and $θ$ is the angle created on the complex plane.

$z = a + b i = | z | (\cos (θ) + i \sin (θ))$

Step 2

The modulus of a complex number is the distance from the origin on the complex plane.

$| z | = \sqrt{a^{2} + b^{2}}$ where $z = a + b i$

Step 3

Substitute the actual values of $a = - 1$ and $b = 0$ .

$| z | = \sqrt{0^{2} + {(- 1)}^{2}}$

Step 4

Find $| z |$ .

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Step 4.1

Raising $0$ to any positive power yields $0$ .

$| z | = \sqrt{0 + {(- 1)}^{2}}$

Step 4.2

Raise $- 1$ to the power of $2$ .

$| z | = \sqrt{0 + 1}$

Step 4.3

Add $0$ and $1$ .

$| z | = \sqrt{1}$

Step 4.4

Any root of $1$ is $1$ .

$| z | = 1$

Step 5

The angle of the point on the complex plane is the inverse tangent of the complex portion over the real portion.

$θ = \arctan (\frac{0}{- 1})$

Step 6

Since inverse tangent of $\frac{0}{- 1}$ produces an angle in the second quadrant, the value of the angle is $π$ .

$θ = π$

Step 7

Substitute the values of $θ = π$ and $| z | = 1$ .

$\cos (π) + i \sin (π)$