Linear Algebra Examples

$- 7 + 7 i$

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 $a = - 7$ and $b = 7$ .

$| z | = \sqrt{7^{2} + {(- 7)}^{2}}$

Step 4

Find $| z |$ .

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Step 4.1

Raise $7$ to the power of $2$ .

$| z | = \sqrt{49 + {(- 7)}^{2}}$

Step 4.2

Raise $- 7$ to the power of $2$ .

$| z | = \sqrt{49 + 49}$

Step 4.3

Add $49$ and $49$ .

$| z | = \sqrt{98}$

Step 4.4

Rewrite $98$ as $7^{2} \cdot 2$ .

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Step 4.4.1

Factor $49$ out of $98$ .

$| z | = \sqrt{49 (2)}$

Step 4.4.2

Rewrite $49$ as $7^{2}$ .

$| z | = \sqrt{7^{2} \cdot 2}$

Step 4.5

Pull terms out from under the radical.

$| z | = 7 \sqrt{2}$

Step 5

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

$θ = \arctan (\frac{7}{- 7})$

Step 6

Since inverse tangent of $\frac{7}{- 7}$ produces an angle in the second quadrant, the value of the angle is $\frac{3 π}{4}$ .

$θ = \frac{3 π}{4}$

Step 7

Substitute the values of $θ = \frac{3 π}{4}$ and $| z | = 7 \sqrt{2}$ .

$7 \sqrt{2} (\cos (\frac{3 π}{4}) + i \sin (\frac{3 π}{4}))$