Trigonometry Examples

$\sqrt{3} + 3 i$

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 $a = \sqrt{3}$ and $b = 3$ .

$| z | = \sqrt{3^{2} + {(\sqrt{3})}^{2}}$

Step 4

Find $| z |$ .

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Step 4.1

Raise $3$ to the power of $2$ .

$| z | = \sqrt{9 + {(\sqrt{3})}^{2}}$

Step 4.2

Rewrite ${\sqrt{3}}^{2}$ as $3$ .

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Step 4.2.1

Use $\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite $\sqrt{3}$ as $3^{\frac{1}{2}}$ .

$| z | = \sqrt{9 + {(3^{\frac{1}{2}})}^{2}}$

Step 4.2.2

Apply the power rule and multiply exponents, ${(a^{m})}^{n} = a^{m n}$ .

$| z | = \sqrt{9 + 3^{\frac{1}{2} \cdot 2}}$

Step 4.2.3

Combine $\frac{1}{2}$ and $2$ .

$| z | = \sqrt{9 + 3^{\frac{2}{2}}}$

Step 4.2.4

Cancel the common factor of $2$ .

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Step 4.2.4.1

Cancel the common factor.

$| z | = \sqrt{9 + 3^{\frac{2}{2}}}$

Step 4.2.4.2

Rewrite the expression.

$| z | = \sqrt{9 + 3}$

Step 4.2.5

Evaluate the exponent.

$| z | = \sqrt{9 + 3}$

Step 4.3

Add $9$ and $3$ .

$| z | = \sqrt{12}$

Step 4.4

Rewrite $12$ as $2^{2} \cdot 3$ .

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Step 4.4.1

Factor $4$ out of $12$ .

$| z | = \sqrt{4 (3)}$

Step 4.4.2

Rewrite $4$ as $2^{2}$ .

$| z | = \sqrt{2^{2} \cdot 3}$

Step 4.5

Pull terms out from under the radical.

$| z | = 2 \sqrt{3}$

Step 5

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

$θ = \arctan (\frac{3}{\sqrt{3}})$

Step 6

Since inverse tangent of $\frac{3}{\sqrt{3}}$ produces an angle in the first quadrant, the value of the angle is $\frac{π}{3}$ .

$θ = \frac{π}{3}$

Step 7

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

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