Trigonometry Examples

${(3 (\cos (20) + i \sin (20)))}^{4}$

Step 1

Apply the distributive property.

${(3 \cos (20) + 3 (i \sin (20)))}^{4}$

Step 2

Use the Binomial Theorem.

${(3 \cos (20))}^{4} + 4 {(3 \cos (20))}^{3} (3 i \sin (20)) + 6 {(3 \cos (20))}^{2} {(3 i \sin (20))}^{2} + 4 (3 \cos (20)) {(3 i \sin (20))}^{3} + {(3 i \sin (20))}^{4}$

Step 3

Simplify terms.

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Step 3.1

Simplify each term.

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Step 3.1.1

Apply the product rule to $3 \cos (20)$ .

$3^{4} \cos^{4} (20) + 4 {(3 \cos (20))}^{3} (3 i \sin (20)) + 6 {(3 \cos (20))}^{2} {(3 i \sin (20))}^{2} + 4 (3 \cos (20)) {(3 i \sin (20))}^{3} + {(3 i \sin (20))}^{4}$

Step 3.1.2

Raise $3$ to the power of $4$ .

$81 \cos^{4} (20) + 4 {(3 \cos (20))}^{3} (3 i \sin (20)) + 6 {(3 \cos (20))}^{2} {(3 i \sin (20))}^{2} + 4 (3 \cos (20)) {(3 i \sin (20))}^{3} + {(3 i \sin (20))}^{4}$

Step 3.1.3

Apply the product rule to $3 \cos (20)$ .

$81 \cos^{4} (20) + 4 (3^{3} \cos^{3} (20)) (3 i \sin (20)) + 6 {(3 \cos (20))}^{2} {(3 i \sin (20))}^{2} + 4 (3 \cos (20)) {(3 i \sin (20))}^{3} + {(3 i \sin (20))}^{4}$

Step 3.1.4

Multiply $3^{3}$ by $3$ by adding the exponents.

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Step 3.1.4.1

Move $3$ .

$81 \cos^{4} (20) + 4 (3 \cdot 3^{3} \cos^{3} (20)) (i \sin (20)) + 6 {(3 \cos (20))}^{2} {(3 i \sin (20))}^{2} + 4 (3 \cos (20)) {(3 i \sin (20))}^{3} + {(3 i \sin (20))}^{4}$

Step 3.1.4.2

Multiply $3$ by $3^{3}$ .

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Step 3.1.4.2.1

Raise $3$ to the power of $1$ .

$81 \cos^{4} (20) + 4 (3^{1} \cdot 3^{3} \cos^{3} (20)) (i \sin (20)) + 6 {(3 \cos (20))}^{2} {(3 i \sin (20))}^{2} + 4 (3 \cos (20)) {(3 i \sin (20))}^{3} + {(3 i \sin (20))}^{4}$

Step 3.1.4.2.2

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$81 \cos^{4} (20) + 4 (3^{1 + 3} \cos^{3} (20)) (i \sin (20)) + 6 {(3 \cos (20))}^{2} {(3 i \sin (20))}^{2} + 4 (3 \cos (20)) {(3 i \sin (20))}^{3} + {(3 i \sin (20))}^{4}$

Step 3.1.4.3

Add $1$ and $3$ .

$81 \cos^{4} (20) + 4 (3^{4} \cos^{3} (20)) (i \sin (20)) + 6 {(3 \cos (20))}^{2} {(3 i \sin (20))}^{2} + 4 (3 \cos (20)) {(3 i \sin (20))}^{3} + {(3 i \sin (20))}^{4}$

Step 3.1.5

Raise $3$ to the power of $4$ .

$81 \cos^{4} (20) + 4 (81 \cos^{3} (20)) (i \sin (20)) + 6 {(3 \cos (20))}^{2} {(3 i \sin (20))}^{2} + 4 (3 \cos (20)) {(3 i \sin (20))}^{3} + {(3 i \sin (20))}^{4}$

Step 3.1.6

Multiply $81$ by $4$ .

$81 \cos^{4} (20) + 324 \cos^{3} (20) (i \sin (20)) + 6 {(3 \cos (20))}^{2} {(3 i \sin (20))}^{2} + 4 (3 \cos (20)) {(3 i \sin (20))}^{3} + {(3 i \sin (20))}^{4}$

Step 3.1.7

Apply the product rule to $3 \cos (20)$ .

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) + 6 (3^{2} \cos^{2} (20)) {(3 i \sin (20))}^{2} + 4 (3 \cos (20)) {(3 i \sin (20))}^{3} + {(3 i \sin (20))}^{4}$

Step 3.1.8

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

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) + 6 (9 \cos^{2} (20)) {(3 i \sin (20))}^{2} + 4 (3 \cos (20)) {(3 i \sin (20))}^{3} + {(3 i \sin (20))}^{4}$

Step 3.1.9

Multiply $9$ by $6$ .

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) + 54 \cos^{2} (20) {(3 i \sin (20))}^{2} + 4 (3 \cos (20)) {(3 i \sin (20))}^{3} + {(3 i \sin (20))}^{4}$

Step 3.1.10

Use the power rule ${(a b)}^{n} = a^{n} b^{n}$ to distribute the exponent.

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Step 3.1.10.1

Apply the product rule to $3 i \sin (20)$ .

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) + 54 \cos^{2} (20) ({(3 i)}^{2} \sin^{2} (20)) + 4 (3 \cos (20)) {(3 i \sin (20))}^{3} + {(3 i \sin (20))}^{4}$

Step 3.1.10.2

Apply the product rule to $3 i$ .

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) + 54 \cos^{2} (20) (3^{2} i^{2} \sin^{2} (20)) + 4 (3 \cos (20)) {(3 i \sin (20))}^{3} + {(3 i \sin (20))}^{4}$

Step 3.1.11

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

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) + 54 \cos^{2} (20) (9 i^{2} \sin^{2} (20)) + 4 (3 \cos (20)) {(3 i \sin (20))}^{3} + {(3 i \sin (20))}^{4}$

Step 3.1.12

Rewrite $i^{2}$ as $- 1$ .

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) + 54 \cos^{2} (20) (9 \cdot - 1 \sin^{2} (20)) + 4 (3 \cos (20)) {(3 i \sin (20))}^{3} + {(3 i \sin (20))}^{4}$

Step 3.1.13

Multiply $9$ by $- 1$ .

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) + 54 \cos^{2} (20) (- 9 \sin^{2} (20)) + 4 (3 \cos (20)) {(3 i \sin (20))}^{3} + {(3 i \sin (20))}^{4}$

Step 3.1.14

Multiply $- 9$ by $54$ .

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) - 486 \cos^{2} (20) \sin^{2} (20) + 4 (3 \cos (20)) {(3 i \sin (20))}^{3} + {(3 i \sin (20))}^{4}$

Step 3.1.15

Multiply $3$ by $4$ .

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) - 486 \cos^{2} (20) \sin^{2} (20) + 12 \cos (20) {(3 i \sin (20))}^{3} + {(3 i \sin (20))}^{4}$

Step 3.1.16

Use the power rule ${(a b)}^{n} = a^{n} b^{n}$ to distribute the exponent.

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Step 3.1.16.1

Apply the product rule to $3 i \sin (20)$ .

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) - 486 \cos^{2} (20) \sin^{2} (20) + 12 \cos (20) ({(3 i)}^{3} \sin^{3} (20)) + {(3 i \sin (20))}^{4}$

Step 3.1.16.2

Apply the product rule to $3 i$ .

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) - 486 \cos^{2} (20) \sin^{2} (20) + 12 \cos (20) (3^{3} i^{3} \sin^{3} (20)) + {(3 i \sin (20))}^{4}$

Step 3.1.17

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

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) - 486 \cos^{2} (20) \sin^{2} (20) + 12 \cos (20) (27 i^{3} \sin^{3} (20)) + {(3 i \sin (20))}^{4}$

Step 3.1.18

Factor out $i^{2}$ .

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) - 486 \cos^{2} (20) \sin^{2} (20) + 12 \cos (20) (27 (i^{2} \cdot i) \sin^{3} (20)) + {(3 i \sin (20))}^{4}$

Step 3.1.19

Rewrite $i^{2}$ as $- 1$ .

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) - 486 \cos^{2} (20) \sin^{2} (20) + 12 \cos (20) (27 (- 1 \cdot i) \sin^{3} (20)) + {(3 i \sin (20))}^{4}$

Step 3.1.20

Rewrite $- 1 i$ as $- i$ .

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) - 486 \cos^{2} (20) \sin^{2} (20) + 12 \cos (20) (27 (- i) \sin^{3} (20)) + {(3 i \sin (20))}^{4}$

Step 3.1.21

Multiply $- 1$ by $27$ .

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) - 486 \cos^{2} (20) \sin^{2} (20) + 12 \cos (20) (- 27 i \sin^{3} (20)) + {(3 i \sin (20))}^{4}$

Step 3.1.22

Multiply $- 27$ by $12$ .

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) - 486 \cos^{2} (20) \sin^{2} (20) - 324 \cos (20) (i \sin^{3} (20)) + {(3 i \sin (20))}^{4}$

Step 3.1.23

Use the power rule ${(a b)}^{n} = a^{n} b^{n}$ to distribute the exponent.

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Step 3.1.23.1

Apply the product rule to $3 i \sin (20)$ .

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) - 486 \cos^{2} (20) \sin^{2} (20) - 324 \cos (20) i \sin^{3} (20) + {(3 i)}^{4} \sin^{4} (20)$

Step 3.1.23.2

Apply the product rule to $3 i$ .

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) - 486 \cos^{2} (20) \sin^{2} (20) - 324 \cos (20) i \sin^{3} (20) + 3^{4} i^{4} \sin^{4} (20)$

Step 3.1.24

Raise $3$ to the power of $4$ .

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) - 486 \cos^{2} (20) \sin^{2} (20) - 324 \cos (20) i \sin^{3} (20) + 81 i^{4} \sin^{4} (20)$

Step 3.1.25

Rewrite $i^{4}$ as $1$ .

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Step 3.1.25.1

Rewrite $i^{4}$ as ${(i^{2})}^{2}$ .

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) - 486 \cos^{2} (20) \sin^{2} (20) - 324 \cos (20) i \sin^{3} (20) + 81 {(i^{2})}^{2} \sin^{4} (20)$

Step 3.1.25.2

Rewrite $i^{2}$ as $- 1$ .

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) - 486 \cos^{2} (20) \sin^{2} (20) - 324 \cos (20) i \sin^{3} (20) + 81 {(- 1)}^{2} \sin^{4} (20)$

Step 3.1.25.3

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

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) - 486 \cos^{2} (20) \sin^{2} (20) - 324 \cos (20) i \sin^{3} (20) + 81 \cdot 1 \sin^{4} (20)$

Step 3.1.26

Multiply $81$ by $1$ .

$81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) - 486 \cos^{2} (20) \sin^{2} (20) - 324 \cos (20) i \sin^{3} (20) + 81 \sin^{4} (20)$

Step 3.2

Simplify the expression.

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Step 3.2.1

Reorder factors in $81 \cos^{4} (20) + 324 \cos^{3} (20) i \sin (20) - 486 \cos^{2} (20) \sin^{2} (20) - 324 \cos (20) i \sin^{3} (20) + 81 \sin^{4} (20)$ .

$81 \cos^{4} (20) + 324 i \cos^{3} (20) \sin (20) - 486 \cos^{2} (20) \sin^{2} (20) - 324 i \cos (20) \sin^{3} (20) + 81 \sin^{4} (20)$

Step 3.2.2

Reorder $81 \cos^{4} (20) + 324 i \cos^{3} (20) \sin (20)$ and $- 486 \cos^{2} (20) \sin^{2} (20)$ .

$- 486 \cos^{2} (20) \sin^{2} (20) + 81 \cos^{4} (20) + 324 i \cos^{3} (20) \sin (20) - 324 i \cos (20) \sin^{3} (20) + 81 \sin^{4} (20)$

Step 3.2.3

Reorder $- 486 \cos^{2} (20) \sin^{2} (20) + 81 \cos^{4} (20) + 324 i \cos^{3} (20) \sin (20) - 324 i \cos (20) \sin^{3} (20)$ and $81 \sin^{4} (20)$ .

$81 \sin^{4} (20) - 486 \cos^{2} (20) \sin^{2} (20) + 81 \cos^{4} (20) + 324 i \cos^{3} (20) \sin (20) - 324 i \cos (20) \sin^{3} (20)$