Precalculus Examples

$\cos (5 x) + \cos (8 x)$

Step 1

Factor $2$ out of $8 x$ .

$\cos (5 x) + \cos (2 (4 x))$

Step 2

Simplify each term.

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Step 2.1

Factor $2$ out of $4 x$ .

$\cos (5 x) + 2 \cos^{2} (2 (2 x)) - 1$

Step 2.2

Simplify each term.

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Step 2.2.1

Use the double-angle identity to transform $\cos (2 x)$ to $2 \cos^{2} (x) - 1$ .

$\cos (5 x) + 2 {(2 {(2 \cos^{2} (x) - 1)}^{2} - 1)}^{2} - 1$

Step 2.2.2

Rewrite ${(2 \cos^{2} (x) - 1)}^{2}$ as $(2 \cos^{2} (x) - 1) (2 \cos^{2} (x) - 1)$ .

$\cos (5 x) + 2 {(2 ((2 \cos^{2} (x) - 1) (2 \cos^{2} (x) - 1)) - 1)}^{2} - 1$

Step 2.2.3

Expand $(2 \cos^{2} (x) - 1) (2 \cos^{2} (x) - 1)$ using the FOIL Method.

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Step 2.2.3.1

Apply the distributive property.

$\cos (5 x) + 2 {(2 (2 \cos^{2} (x) (2 \cos^{2} (x) - 1) - 1 (2 \cos^{2} (x) - 1)) - 1)}^{2} - 1$

Step 2.2.3.2

Apply the distributive property.

$\cos (5 x) + 2 {(2 (2 \cos^{2} (x) (2 \cos^{2} (x)) + 2 \cos^{2} (x) \cdot - 1 - 1 (2 \cos^{2} (x) - 1)) - 1)}^{2} - 1$

Step 2.2.3.3

Apply the distributive property.

$\cos (5 x) + 2 {(2 (2 \cos^{2} (x) (2 \cos^{2} (x)) + 2 \cos^{2} (x) \cdot - 1 - 1 (2 \cos^{2} (x)) - 1 \cdot - 1) - 1)}^{2} - 1$

Step 2.2.4

Simplify and combine like terms.

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Step 2.2.4.1

Simplify each term.

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Step 2.2.4.1.1

Rewrite using the commutative property of multiplication.

$\cos (5 x) + 2 {(2 (2 \cdot 2 \cos^{2} (x) \cos^{2} (x) + 2 \cos^{2} (x) \cdot - 1 - 1 (2 \cos^{2} (x)) - 1 \cdot - 1) - 1)}^{2} - 1$

Step 2.2.4.1.2

Multiply $\cos^{2} (x)$ by $\cos^{2} (x)$ by adding the exponents.

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Step 2.2.4.1.2.1

Move $\cos^{2} (x)$ .

$\cos (5 x) + 2 {(2 (2 \cdot 2 (\cos^{2} (x) \cos^{2} (x)) + 2 \cos^{2} (x) \cdot - 1 - 1 (2 \cos^{2} (x)) - 1 \cdot - 1) - 1)}^{2} - 1$

Step 2.2.4.1.2.2

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

$\cos (5 x) + 2 {(2 (2 \cdot 2 {\cos (x)}^{2 + 2} + 2 \cos^{2} (x) \cdot - 1 - 1 (2 \cos^{2} (x)) - 1 \cdot - 1) - 1)}^{2} - 1$

Step 2.2.4.1.2.3

Add $2$ and $2$ .

$\cos (5 x) + 2 {(2 (2 \cdot 2 \cos^{4} (x) + 2 \cos^{2} (x) \cdot - 1 - 1 (2 \cos^{2} (x)) - 1 \cdot - 1) - 1)}^{2} - 1$

Step 2.2.4.1.3

Multiply $2$ by $2$ .

$\cos (5 x) + 2 {(2 (4 \cos^{4} (x) + 2 \cos^{2} (x) \cdot - 1 - 1 (2 \cos^{2} (x)) - 1 \cdot - 1) - 1)}^{2} - 1$

Step 2.2.4.1.4

Multiply $- 1$ by $2$ .

$\cos (5 x) + 2 {(2 (4 \cos^{4} (x) - 2 \cos^{2} (x) - 1 (2 \cos^{2} (x)) - 1 \cdot - 1) - 1)}^{2} - 1$

Step 2.2.4.1.5

Multiply $2$ by $- 1$ .

$\cos (5 x) + 2 {(2 (4 \cos^{4} (x) - 2 \cos^{2} (x) - 2 \cos^{2} (x) - 1 \cdot - 1) - 1)}^{2} - 1$

Step 2.2.4.1.6

Multiply $- 1$ by $- 1$ .

$\cos (5 x) + 2 {(2 (4 \cos^{4} (x) - 2 \cos^{2} (x) - 2 \cos^{2} (x) + 1) - 1)}^{2} - 1$

Step 2.2.4.2

Subtract $2 \cos^{2} (x)$ from $- 2 \cos^{2} (x)$ .

$\cos (5 x) + 2 {(2 (4 \cos^{4} (x) - 4 \cos^{2} (x) + 1) - 1)}^{2} - 1$

Step 2.2.5

Apply the distributive property.

$\cos (5 x) + 2 {(2 (4 \cos^{4} (x)) + 2 (- 4 \cos^{2} (x)) + 2 \cdot 1 - 1)}^{2} - 1$

Step 2.2.6

Simplify.

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Step 2.2.6.1

Multiply $4$ by $2$ .

$\cos (5 x) + 2 {(8 \cos^{4} (x) + 2 (- 4 \cos^{2} (x)) + 2 \cdot 1 - 1)}^{2} - 1$

Step 2.2.6.2

Multiply $- 4$ by $2$ .

$\cos (5 x) + 2 {(8 \cos^{4} (x) - 8 \cos^{2} (x) + 2 \cdot 1 - 1)}^{2} - 1$

Step 2.2.6.3

Multiply $2$ by $1$ .

$\cos (5 x) + 2 {(8 \cos^{4} (x) - 8 \cos^{2} (x) + 2 - 1)}^{2} - 1$

Step 2.3

Subtract $1$ from $2$ .

$\cos (5 x) + 2 {(8 \cos^{4} (x) - 8 \cos^{2} (x) + 1)}^{2} - 1$

Step 2.4

Rewrite ${(8 \cos^{4} (x) - 8 \cos^{2} (x) + 1)}^{2}$ as $(8 \cos^{4} (x) - 8 \cos^{2} (x) + 1) (8 \cos^{4} (x) - 8 \cos^{2} (x) + 1)$ .

$\cos (5 x) + 2 ((8 \cos^{4} (x) - 8 \cos^{2} (x) + 1) (8 \cos^{4} (x) - 8 \cos^{2} (x) + 1)) - 1$

Step 2.5

Expand $(8 \cos^{4} (x) - 8 \cos^{2} (x) + 1) (8 \cos^{4} (x) - 8 \cos^{2} (x) + 1)$ by multiplying each term in the first expression by each term in the second expression.

$\cos (5 x) + 2 (8 \cos^{4} (x) (8 \cos^{4} (x)) + 8 \cos^{4} (x) (- 8 \cos^{2} (x)) + 8 \cos^{4} (x) \cdot 1 - 8 \cos^{2} (x) (8 \cos^{4} (x)) - 8 \cos^{2} (x) (- 8 \cos^{2} (x)) - 8 \cos^{2} (x) \cdot 1 + 1 (8 \cos^{4} (x)) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6

Simplify each term.

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Step 2.6.1

Rewrite using the commutative property of multiplication.

$\cos (5 x) + 2 (8 \cdot 8 \cos^{4} (x) \cos^{4} (x) + 8 \cos^{4} (x) (- 8 \cos^{2} (x)) + 8 \cos^{4} (x) \cdot 1 - 8 \cos^{2} (x) (8 \cos^{4} (x)) - 8 \cos^{2} (x) (- 8 \cos^{2} (x)) - 8 \cos^{2} (x) \cdot 1 + 1 (8 \cos^{4} (x)) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6.2

Multiply $\cos^{4} (x)$ by $\cos^{4} (x)$ by adding the exponents.

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Step 2.6.2.1

Move $\cos^{4} (x)$ .

$\cos (5 x) + 2 (8 \cdot 8 (\cos^{4} (x) \cos^{4} (x)) + 8 \cos^{4} (x) (- 8 \cos^{2} (x)) + 8 \cos^{4} (x) \cdot 1 - 8 \cos^{2} (x) (8 \cos^{4} (x)) - 8 \cos^{2} (x) (- 8 \cos^{2} (x)) - 8 \cos^{2} (x) \cdot 1 + 1 (8 \cos^{4} (x)) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6.2.2

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

$\cos (5 x) + 2 (8 \cdot 8 {\cos (x)}^{4 + 4} + 8 \cos^{4} (x) (- 8 \cos^{2} (x)) + 8 \cos^{4} (x) \cdot 1 - 8 \cos^{2} (x) (8 \cos^{4} (x)) - 8 \cos^{2} (x) (- 8 \cos^{2} (x)) - 8 \cos^{2} (x) \cdot 1 + 1 (8 \cos^{4} (x)) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6.2.3

Add $4$ and $4$ .

$\cos (5 x) + 2 (8 \cdot 8 \cos^{8} (x) + 8 \cos^{4} (x) (- 8 \cos^{2} (x)) + 8 \cos^{4} (x) \cdot 1 - 8 \cos^{2} (x) (8 \cos^{4} (x)) - 8 \cos^{2} (x) (- 8 \cos^{2} (x)) - 8 \cos^{2} (x) \cdot 1 + 1 (8 \cos^{4} (x)) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6.3

Multiply $8$ by $8$ .

$\cos (5 x) + 2 (64 \cos^{8} (x) + 8 \cos^{4} (x) (- 8 \cos^{2} (x)) + 8 \cos^{4} (x) \cdot 1 - 8 \cos^{2} (x) (8 \cos^{4} (x)) - 8 \cos^{2} (x) (- 8 \cos^{2} (x)) - 8 \cos^{2} (x) \cdot 1 + 1 (8 \cos^{4} (x)) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6.4

Rewrite using the commutative property of multiplication.

$\cos (5 x) + 2 (64 \cos^{8} (x) + 8 \cdot - 8 \cos^{4} (x) \cos^{2} (x) + 8 \cos^{4} (x) \cdot 1 - 8 \cos^{2} (x) (8 \cos^{4} (x)) - 8 \cos^{2} (x) (- 8 \cos^{2} (x)) - 8 \cos^{2} (x) \cdot 1 + 1 (8 \cos^{4} (x)) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6.5

Multiply $\cos^{4} (x)$ by $\cos^{2} (x)$ by adding the exponents.

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Step 2.6.5.1

Move $\cos^{2} (x)$ .

$\cos (5 x) + 2 (64 \cos^{8} (x) + 8 \cdot - 8 (\cos^{2} (x) \cos^{4} (x)) + 8 \cos^{4} (x) \cdot 1 - 8 \cos^{2} (x) (8 \cos^{4} (x)) - 8 \cos^{2} (x) (- 8 \cos^{2} (x)) - 8 \cos^{2} (x) \cdot 1 + 1 (8 \cos^{4} (x)) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6.5.2

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

$\cos (5 x) + 2 (64 \cos^{8} (x) + 8 \cdot - 8 {\cos (x)}^{2 + 4} + 8 \cos^{4} (x) \cdot 1 - 8 \cos^{2} (x) (8 \cos^{4} (x)) - 8 \cos^{2} (x) (- 8 \cos^{2} (x)) - 8 \cos^{2} (x) \cdot 1 + 1 (8 \cos^{4} (x)) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6.5.3

Add $2$ and $4$ .

$\cos (5 x) + 2 (64 \cos^{8} (x) + 8 \cdot - 8 \cos^{6} (x) + 8 \cos^{4} (x) \cdot 1 - 8 \cos^{2} (x) (8 \cos^{4} (x)) - 8 \cos^{2} (x) (- 8 \cos^{2} (x)) - 8 \cos^{2} (x) \cdot 1 + 1 (8 \cos^{4} (x)) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6.6

Multiply $8$ by $- 8$ .

$\cos (5 x) + 2 (64 \cos^{8} (x) - 64 \cos^{6} (x) + 8 \cos^{4} (x) \cdot 1 - 8 \cos^{2} (x) (8 \cos^{4} (x)) - 8 \cos^{2} (x) (- 8 \cos^{2} (x)) - 8 \cos^{2} (x) \cdot 1 + 1 (8 \cos^{4} (x)) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6.7

Multiply $8$ by $1$ .

$\cos (5 x) + 2 (64 \cos^{8} (x) - 64 \cos^{6} (x) + 8 \cos^{4} (x) - 8 \cos^{2} (x) (8 \cos^{4} (x)) - 8 \cos^{2} (x) (- 8 \cos^{2} (x)) - 8 \cos^{2} (x) \cdot 1 + 1 (8 \cos^{4} (x)) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6.8

Rewrite using the commutative property of multiplication.

$\cos (5 x) + 2 (64 \cos^{8} (x) - 64 \cos^{6} (x) + 8 \cos^{4} (x) - 8 \cdot 8 \cos^{2} (x) \cos^{4} (x) - 8 \cos^{2} (x) (- 8 \cos^{2} (x)) - 8 \cos^{2} (x) \cdot 1 + 1 (8 \cos^{4} (x)) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6.9

Multiply $\cos^{2} (x)$ by $\cos^{4} (x)$ by adding the exponents.

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Step 2.6.9.1

Move $\cos^{4} (x)$ .

$\cos (5 x) + 2 (64 \cos^{8} (x) - 64 \cos^{6} (x) + 8 \cos^{4} (x) - 8 \cdot 8 (\cos^{4} (x) \cos^{2} (x)) - 8 \cos^{2} (x) (- 8 \cos^{2} (x)) - 8 \cos^{2} (x) \cdot 1 + 1 (8 \cos^{4} (x)) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6.9.2

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

$\cos (5 x) + 2 (64 \cos^{8} (x) - 64 \cos^{6} (x) + 8 \cos^{4} (x) - 8 \cdot 8 {\cos (x)}^{4 + 2} - 8 \cos^{2} (x) (- 8 \cos^{2} (x)) - 8 \cos^{2} (x) \cdot 1 + 1 (8 \cos^{4} (x)) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6.9.3

Add $4$ and $2$ .

$\cos (5 x) + 2 (64 \cos^{8} (x) - 64 \cos^{6} (x) + 8 \cos^{4} (x) - 8 \cdot 8 \cos^{6} (x) - 8 \cos^{2} (x) (- 8 \cos^{2} (x)) - 8 \cos^{2} (x) \cdot 1 + 1 (8 \cos^{4} (x)) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6.10

Multiply $- 8$ by $8$ .

$\cos (5 x) + 2 (64 \cos^{8} (x) - 64 \cos^{6} (x) + 8 \cos^{4} (x) - 64 \cos^{6} (x) - 8 \cos^{2} (x) (- 8 \cos^{2} (x)) - 8 \cos^{2} (x) \cdot 1 + 1 (8 \cos^{4} (x)) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6.11

Rewrite using the commutative property of multiplication.

$\cos (5 x) + 2 (64 \cos^{8} (x) - 64 \cos^{6} (x) + 8 \cos^{4} (x) - 64 \cos^{6} (x) - 8 \cdot - 8 \cos^{2} (x) \cos^{2} (x) - 8 \cos^{2} (x) \cdot 1 + 1 (8 \cos^{4} (x)) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6.12

Multiply $\cos^{2} (x)$ by $\cos^{2} (x)$ by adding the exponents.

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Step 2.6.12.1

Move $\cos^{2} (x)$ .

$\cos (5 x) + 2 (64 \cos^{8} (x) - 64 \cos^{6} (x) + 8 \cos^{4} (x) - 64 \cos^{6} (x) - 8 \cdot - 8 (\cos^{2} (x) \cos^{2} (x)) - 8 \cos^{2} (x) \cdot 1 + 1 (8 \cos^{4} (x)) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6.12.2

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

$\cos (5 x) + 2 (64 \cos^{8} (x) - 64 \cos^{6} (x) + 8 \cos^{4} (x) - 64 \cos^{6} (x) - 8 \cdot - 8 {\cos (x)}^{2 + 2} - 8 \cos^{2} (x) \cdot 1 + 1 (8 \cos^{4} (x)) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6.12.3

Add $2$ and $2$ .

$\cos (5 x) + 2 (64 \cos^{8} (x) - 64 \cos^{6} (x) + 8 \cos^{4} (x) - 64 \cos^{6} (x) - 8 \cdot - 8 \cos^{4} (x) - 8 \cos^{2} (x) \cdot 1 + 1 (8 \cos^{4} (x)) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6.13

Multiply $- 8$ by $- 8$ .

$\cos (5 x) + 2 (64 \cos^{8} (x) - 64 \cos^{6} (x) + 8 \cos^{4} (x) - 64 \cos^{6} (x) + 64 \cos^{4} (x) - 8 \cos^{2} (x) \cdot 1 + 1 (8 \cos^{4} (x)) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6.14

Multiply $- 8$ by $1$ .

$\cos (5 x) + 2 (64 \cos^{8} (x) - 64 \cos^{6} (x) + 8 \cos^{4} (x) - 64 \cos^{6} (x) + 64 \cos^{4} (x) - 8 \cos^{2} (x) + 1 (8 \cos^{4} (x)) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6.15

Multiply $8 \cos^{4} (x)$ by $1$ .

$\cos (5 x) + 2 (64 \cos^{8} (x) - 64 \cos^{6} (x) + 8 \cos^{4} (x) - 64 \cos^{6} (x) + 64 \cos^{4} (x) - 8 \cos^{2} (x) + 8 \cos^{4} (x) + 1 (- 8 \cos^{2} (x)) + 1 \cdot 1) - 1$

Step 2.6.16

Multiply $- 8 \cos^{2} (x)$ by $1$ .

$\cos (5 x) + 2 (64 \cos^{8} (x) - 64 \cos^{6} (x) + 8 \cos^{4} (x) - 64 \cos^{6} (x) + 64 \cos^{4} (x) - 8 \cos^{2} (x) + 8 \cos^{4} (x) - 8 \cos^{2} (x) + 1 \cdot 1) - 1$

Step 2.6.17

Multiply $1$ by $1$ .

$\cos (5 x) + 2 (64 \cos^{8} (x) - 64 \cos^{6} (x) + 8 \cos^{4} (x) - 64 \cos^{6} (x) + 64 \cos^{4} (x) - 8 \cos^{2} (x) + 8 \cos^{4} (x) - 8 \cos^{2} (x) + 1) - 1$

Step 2.7

Subtract $64 \cos^{6} (x)$ from $- 64 \cos^{6} (x)$ .

$\cos (5 x) + 2 (64 \cos^{8} (x) - 128 \cos^{6} (x) + 8 \cos^{4} (x) + 64 \cos^{4} (x) - 8 \cos^{2} (x) + 8 \cos^{4} (x) - 8 \cos^{2} (x) + 1) - 1$

Step 2.8

Add $8 \cos^{4} (x)$ and $64 \cos^{4} (x)$ .

$\cos (5 x) + 2 (64 \cos^{8} (x) - 128 \cos^{6} (x) + 72 \cos^{4} (x) - 8 \cos^{2} (x) + 8 \cos^{4} (x) - 8 \cos^{2} (x) + 1) - 1$

Step 2.9

Add $72 \cos^{4} (x)$ and $8 \cos^{4} (x)$ .

$\cos (5 x) + 2 (64 \cos^{8} (x) - 128 \cos^{6} (x) + 80 \cos^{4} (x) - 8 \cos^{2} (x) - 8 \cos^{2} (x) + 1) - 1$

Step 2.10

Subtract $8 \cos^{2} (x)$ from $- 8 \cos^{2} (x)$ .

$\cos (5 x) + 2 (64 \cos^{8} (x) - 128 \cos^{6} (x) + 80 \cos^{4} (x) - 16 \cos^{2} (x) + 1) - 1$

Step 2.11

Apply the distributive property.

$\cos (5 x) + 2 (64 \cos^{8} (x)) + 2 (- 128 \cos^{6} (x)) + 2 (80 \cos^{4} (x)) + 2 (- 16 \cos^{2} (x)) + 2 \cdot 1 - 1$

Step 2.12

Simplify.

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Step 2.12.1

Multiply $64$ by $2$ .

$\cos (5 x) + 128 \cos^{8} (x) + 2 (- 128 \cos^{6} (x)) + 2 (80 \cos^{4} (x)) + 2 (- 16 \cos^{2} (x)) + 2 \cdot 1 - 1$

Step 2.12.2

Multiply $- 128$ by $2$ .

$\cos (5 x) + 128 \cos^{8} (x) - 256 \cos^{6} (x) + 2 (80 \cos^{4} (x)) + 2 (- 16 \cos^{2} (x)) + 2 \cdot 1 - 1$

Step 2.12.3

Multiply $80$ by $2$ .

$\cos (5 x) + 128 \cos^{8} (x) - 256 \cos^{6} (x) + 160 \cos^{4} (x) + 2 (- 16 \cos^{2} (x)) + 2 \cdot 1 - 1$

Step 2.12.4

Multiply $- 16$ by $2$ .

$\cos (5 x) + 128 \cos^{8} (x) - 256 \cos^{6} (x) + 160 \cos^{4} (x) - 32 \cos^{2} (x) + 2 \cdot 1 - 1$

Step 2.12.5

Multiply $2$ by $1$ .

$\cos (5 x) + 128 \cos^{8} (x) - 256 \cos^{6} (x) + 160 \cos^{4} (x) - 32 \cos^{2} (x) + 2 - 1$

Step 3

Subtract $1$ from $2$ .

$\cos (5 x) + 128 \cos^{8} (x) - 256 \cos^{6} (x) + 160 \cos^{4} (x) - 32 \cos^{2} (x) + 1$