Precalculus Examples

$\sin (4 θ) \cos (2 θ)$

Step 1

Factor $2$ out of $4 θ$ .

$\sin (2 (2 θ)) \cos (2 θ)$

Step 2

Apply the sine double-angle identity.

$2 (2 \sin (θ) \cos (θ)) \cos (2 θ) \cos (2 θ)$

Step 3

Multiply $2$ by $2$ .

$4 (\sin (θ) \cos (θ)) \cos (2 θ) \cos (2 θ)$

Step 4

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

$4 \sin (θ) \cos (θ) (2 \cos^{2} (θ) - 1) \cos (2 θ)$

Step 5

Apply the distributive property.

$(4 \sin (θ) \cos (θ) (2 \cos^{2} (θ)) + 4 \sin (θ) \cos (θ) \cdot - 1) \cos (2 θ)$

Step 6

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

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Step 6.1

Move $\cos^{2} (θ)$ .

$(4 \sin (θ) (\cos^{2} (θ) \cos (θ)) \cdot 2 + 4 \sin (θ) \cos (θ) \cdot - 1) \cos (2 θ)$

Step 6.2

Multiply $\cos^{2} (θ)$ by $\cos (θ)$ .

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Step 6.2.1

Raise $\cos (θ)$ to the power of $1$ .

$(4 \sin (θ) (\cos^{2} (θ) \cos^{1} (θ)) \cdot 2 + 4 \sin (θ) \cos (θ) \cdot - 1) \cos (2 θ)$

Step 6.2.2

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

$(4 \sin (θ) {\cos (θ)}^{2 + 1} \cdot 2 + 4 \sin (θ) \cos (θ) \cdot - 1) \cos (2 θ)$

Step 6.3

Add $2$ and $1$ .

$(4 \sin (θ) \cos^{3} (θ) \cdot 2 + 4 \sin (θ) \cos (θ) \cdot - 1) \cos (2 θ)$

Step 7

Multiply $- 1$ by $4$ .

$(4 \sin (θ) \cos^{3} (θ) \cdot 2 - 4 \sin (θ) \cos (θ)) \cos (2 θ)$

Step 8

Multiply $2$ by $4$ .

$(8 \sin (θ) \cos^{3} (θ) - 4 \sin (θ) \cos (θ)) \cos (2 θ)$

Step 9

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

$(8 \sin (θ) \cos^{3} (θ) - 4 \sin (θ) \cos (θ)) (1 - 2 \sin^{2} (θ))$

Step 10

Expand $(8 \sin (θ) \cos^{3} (θ) - 4 \sin (θ) \cos (θ)) (1 - 2 \sin^{2} (θ))$ using the FOIL Method.

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Step 10.1

Apply the distributive property.

$8 \sin (θ) \cos^{3} (θ) (1 - 2 \sin^{2} (θ)) - 4 \sin (θ) \cos (θ) (1 - 2 \sin^{2} (θ))$

Step 10.2

Apply the distributive property.

$8 \sin (θ) \cos^{3} (θ) \cdot 1 + 8 \sin (θ) \cos^{3} (θ) (- 2 \sin^{2} (θ)) - 4 \sin (θ) \cos (θ) (1 - 2 \sin^{2} (θ))$

Step 10.3

Apply the distributive property.

$8 \sin (θ) \cos^{3} (θ) \cdot 1 + 8 \sin (θ) \cos^{3} (θ) (- 2 \sin^{2} (θ)) - 4 \sin (θ) \cos (θ) \cdot 1 - 4 \sin (θ) \cos (θ) (- 2 \sin^{2} (θ))$

Step 11

Simplify terms.

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Step 11.1

Simplify each term.

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Step 11.1.1

Multiply $8$ by $1$ .

$8 \sin (θ) \cos^{3} (θ) + 8 \sin (θ) \cos^{3} (θ) (- 2 \sin^{2} (θ)) - 4 \sin (θ) \cos (θ) \cdot 1 - 4 \sin (θ) \cos (θ) (- 2 \sin^{2} (θ))$

Step 11.1.2

Multiply $\sin (θ)$ by $\sin^{2} (θ)$ by adding the exponents.

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Step 11.1.2.1

Move $\sin^{2} (θ)$ .

$8 \sin (θ) \cos^{3} (θ) + 8 (\sin^{2} (θ) \sin (θ)) \cos^{3} (θ) \cdot - 2 - 4 \sin (θ) \cos (θ) \cdot 1 - 4 \sin (θ) \cos (θ) (- 2 \sin^{2} (θ))$

Step 11.1.2.2

Multiply $\sin^{2} (θ)$ by $\sin (θ)$ .

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Step 11.1.2.2.1

Raise $\sin (θ)$ to the power of $1$ .

$8 \sin (θ) \cos^{3} (θ) + 8 (\sin^{2} (θ) \sin^{1} (θ)) \cos^{3} (θ) \cdot - 2 - 4 \sin (θ) \cos (θ) \cdot 1 - 4 \sin (θ) \cos (θ) (- 2 \sin^{2} (θ))$

Step 11.1.2.2.2

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

$8 \sin (θ) \cos^{3} (θ) + 8 {\sin (θ)}^{2 + 1} \cos^{3} (θ) \cdot - 2 - 4 \sin (θ) \cos (θ) \cdot 1 - 4 \sin (θ) \cos (θ) (- 2 \sin^{2} (θ))$

Step 11.1.2.3

Add $2$ and $1$ .

$8 \sin (θ) \cos^{3} (θ) + 8 \sin^{3} (θ) \cos^{3} (θ) \cdot - 2 - 4 \sin (θ) \cos (θ) \cdot 1 - 4 \sin (θ) \cos (θ) (- 2 \sin^{2} (θ))$

Step 11.1.3

Multiply $- 2$ by $8$ .

$8 \sin (θ) \cos^{3} (θ) - 16 \sin^{3} (θ) \cos^{3} (θ) - 4 \sin (θ) \cos (θ) \cdot 1 - 4 \sin (θ) \cos (θ) (- 2 \sin^{2} (θ))$

Step 11.1.4

Multiply $- 4$ by $1$ .

$8 \sin (θ) \cos^{3} (θ) - 16 \sin^{3} (θ) \cos^{3} (θ) - 4 \sin (θ) \cos (θ) - 4 \sin (θ) \cos (θ) (- 2 \sin^{2} (θ))$

Step 11.1.5

Multiply $\sin (θ)$ by $\sin^{2} (θ)$ by adding the exponents.

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Step 11.1.5.1

Move $\sin^{2} (θ)$ .

$8 \sin (θ) \cos^{3} (θ) - 16 \sin^{3} (θ) \cos^{3} (θ) - 4 \sin (θ) \cos (θ) - 4 (\sin^{2} (θ) \sin (θ)) \cos (θ) \cdot - 2$

Step 11.1.5.2

Multiply $\sin^{2} (θ)$ by $\sin (θ)$ .

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Step 11.1.5.2.1

Raise $\sin (θ)$ to the power of $1$ .

$8 \sin (θ) \cos^{3} (θ) - 16 \sin^{3} (θ) \cos^{3} (θ) - 4 \sin (θ) \cos (θ) - 4 (\sin^{2} (θ) \sin^{1} (θ)) \cos (θ) \cdot - 2$

Step 11.1.5.2.2

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

$8 \sin (θ) \cos^{3} (θ) - 16 \sin^{3} (θ) \cos^{3} (θ) - 4 \sin (θ) \cos (θ) - 4 {\sin (θ)}^{2 + 1} \cos (θ) \cdot - 2$

Step 11.1.5.3

Add $2$ and $1$ .

$8 \sin (θ) \cos^{3} (θ) - 16 \sin^{3} (θ) \cos^{3} (θ) - 4 \sin (θ) \cos (θ) - 4 \sin^{3} (θ) \cos (θ) \cdot - 2$

Step 11.1.6

Multiply $- 2$ by $- 4$ .

$8 \sin (θ) \cos^{3} (θ) - 16 \sin^{3} (θ) \cos^{3} (θ) - 4 \sin (θ) \cos (θ) + 8 \sin^{3} (θ) \cos (θ)$

Step 11.2

Simplify with factoring out.

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Step 11.2.1

Factor $4 \sin (θ) \cos (θ)$ out of $8 \sin (θ) \cos^{3} (θ) - 16 \sin^{3} (θ) \cos^{3} (θ) - 4 \sin (θ) \cos (θ) + 8 \sin^{3} (θ) \cos (θ)$ .

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Step 11.2.1.1

Factor $4 \sin (θ) \cos (θ)$ out of $8 \sin (θ) \cos^{3} (θ)$ .

$4 \sin (θ) \cos (θ) (2 \cos^{2} (θ)) - 16 \sin^{3} (θ) \cos^{3} (θ) - 4 \sin (θ) \cos (θ) + 8 \sin^{3} (θ) \cos (θ)$

Step 11.2.1.2

Factor $4 \sin (θ) \cos (θ)$ out of $- 16 \sin^{3} (θ) \cos^{3} (θ)$ .

$4 \sin (θ) \cos (θ) (2 \cos^{2} (θ)) + 4 \sin (θ) \cos (θ) (- 4 \sin^{2} (θ) \cos^{2} (θ)) - 4 \sin (θ) \cos (θ) + 8 \sin^{3} (θ) \cos (θ)$

Step 11.2.1.3

Factor $4 \sin (θ) \cos (θ)$ out of $- 4 \sin (θ) \cos (θ)$ .

$4 \sin (θ) \cos (θ) (2 \cos^{2} (θ)) + 4 \sin (θ) \cos (θ) (- 4 \sin^{2} (θ) \cos^{2} (θ)) + 4 \sin (θ) \cos (θ) (- 1) + 8 \sin^{3} (θ) \cos (θ)$

Step 11.2.1.4

Factor $4 \sin (θ) \cos (θ)$ out of $8 \sin^{3} (θ) \cos (θ)$ .

$4 \sin (θ) \cos (θ) (2 \cos^{2} (θ)) + 4 \sin (θ) \cos (θ) (- 4 \sin^{2} (θ) \cos^{2} (θ)) + 4 \sin (θ) \cos (θ) (- 1) + 4 \sin (θ) \cos (θ) (2 \sin^{2} (θ))$

Step 11.2.1.5

Factor $4 \sin (θ) \cos (θ)$ out of $4 \sin (θ) \cos (θ) (2 \cos^{2} (θ)) + 4 \sin (θ) \cos (θ) (- 4 \sin^{2} (θ) \cos^{2} (θ))$ .

$4 \sin (θ) \cos (θ) (2 \cos^{2} (θ) - 4 \sin^{2} (θ) \cos^{2} (θ)) + 4 \sin (θ) \cos (θ) (- 1) + 4 \sin (θ) \cos (θ) (2 \sin^{2} (θ))$

Step 11.2.1.6

Factor $4 \sin (θ) \cos (θ)$ out of $4 \sin (θ) \cos (θ) (2 \cos^{2} (θ) - 4 \sin^{2} (θ) \cos^{2} (θ)) + 4 \sin (θ) \cos (θ) (- 1)$ .

$4 \sin (θ) \cos (θ) (2 \cos^{2} (θ) - 4 \sin^{2} (θ) \cos^{2} (θ) - 1) + 4 \sin (θ) \cos (θ) (2 \sin^{2} (θ))$

Step 11.2.1.7

Factor $4 \sin (θ) \cos (θ)$ out of $4 \sin (θ) \cos (θ) (2 \cos^{2} (θ) - 4 \sin^{2} (θ) \cos^{2} (θ) - 1) + 4 \sin (θ) \cos (θ) (2 \sin^{2} (θ))$ .

$4 \sin (θ) \cos (θ) (2 \cos^{2} (θ) - 4 \sin^{2} (θ) \cos^{2} (θ) - 1 + 2 \sin^{2} (θ))$

Step 11.2.2

Move $2 \sin^{2} (θ)$ .

$4 \sin (θ) \cos (θ) (2 \cos^{2} (θ) + 2 \sin^{2} (θ) - 4 \sin^{2} (θ) \cos^{2} (θ) - 1)$

Step 11.2.3

Factor $2$ out of $2 \cos^{2} (θ)$ .

$4 \sin (θ) \cos (θ) (2 (\cos^{2} (θ)) + 2 \sin^{2} (θ) - 4 \sin^{2} (θ) \cos^{2} (θ) - 1)$

Step 11.2.4

Factor $2$ out of $2 \sin^{2} (θ)$ .

$4 \sin (θ) \cos (θ) (2 (\cos^{2} (θ)) + 2 (\sin^{2} (θ)) - 4 \sin^{2} (θ) \cos^{2} (θ) - 1)$

Step 11.2.5

Factor $2$ out of $2 (\cos^{2} (θ)) + 2 (\sin^{2} (θ))$ .

$4 \sin (θ) \cos (θ) (2 (\cos^{2} (θ) + \sin^{2} (θ)) - 4 \sin^{2} (θ) \cos^{2} (θ) - 1)$

Step 12

Rearrange terms.

$4 \sin (θ) \cos (θ) (2 (\sin^{2} (θ) + \cos^{2} (θ)) - 4 \sin^{2} (θ) \cos^{2} (θ) - 1)$

Step 13

Apply pythagorean identity.

$4 \sin (θ) \cos (θ) (2 \cdot 1 - 4 \sin^{2} (θ) \cos^{2} (θ) - 1)$

Step 14

Simplify by multiplying through.

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Step 14.1

Multiply $2$ by $1$ .

$4 \sin (θ) \cos (θ) (2 - 4 \sin^{2} (θ) \cos^{2} (θ) - 1)$

Step 14.2

Subtract $1$ from $2$ .

$4 \sin (θ) \cos (θ) (- 4 \sin^{2} (θ) \cos^{2} (θ) + 1)$

Step 14.3

Apply the distributive property.

$4 \sin (θ) \cos (θ) (- 4 \sin^{2} (θ) \cos^{2} (θ)) + 4 \sin (θ) \cos (θ) \cdot 1$

Step 15

Multiply $\sin (θ)$ by $\sin^{2} (θ)$ by adding the exponents.

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Step 15.1

Move $\sin^{2} (θ)$ .

$4 (\sin^{2} (θ) \sin (θ)) \cos (θ) (- 4 \cos^{2} (θ)) + 4 \sin (θ) \cos (θ) \cdot 1$

Step 15.2

Multiply $\sin^{2} (θ)$ by $\sin (θ)$ .

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Step 15.2.1

Raise $\sin (θ)$ to the power of $1$ .

$4 (\sin^{2} (θ) \sin^{1} (θ)) \cos (θ) (- 4 \cos^{2} (θ)) + 4 \sin (θ) \cos (θ) \cdot 1$

Step 15.2.2

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

$4 {\sin (θ)}^{2 + 1} \cos (θ) (- 4 \cos^{2} (θ)) + 4 \sin (θ) \cos (θ) \cdot 1$

Step 15.3

Add $2$ and $1$ .

$4 \sin^{3} (θ) \cos (θ) (- 4 \cos^{2} (θ)) + 4 \sin (θ) \cos (θ) \cdot 1$

Step 16

Multiply $4$ by $1$ .

$4 \sin^{3} (θ) \cos (θ) (- 4 \cos^{2} (θ)) + 4 \sin (θ) \cos (θ)$

Step 17

Simplify each term.

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Step 17.1

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

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Step 17.1.1

Move $\cos^{2} (θ)$ .

$4 \sin^{3} (θ) (\cos^{2} (θ) \cos (θ)) \cdot - 4 + 4 \sin (θ) \cos (θ)$

Step 17.1.2

Multiply $\cos^{2} (θ)$ by $\cos (θ)$ .

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Step 17.1.2.1

Raise $\cos (θ)$ to the power of $1$ .

$4 \sin^{3} (θ) (\cos^{2} (θ) \cos^{1} (θ)) \cdot - 4 + 4 \sin (θ) \cos (θ)$

Step 17.1.2.2

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

$4 \sin^{3} (θ) {\cos (θ)}^{2 + 1} \cdot - 4 + 4 \sin (θ) \cos (θ)$

Step 17.1.3

Add $2$ and $1$ .

$4 \sin^{3} (θ) \cos^{3} (θ) \cdot - 4 + 4 \sin (θ) \cos (θ)$

Step 17.2

Multiply $- 4$ by $4$ .

$- 16 \sin^{3} (θ) \cos^{3} (θ) + 4 \sin (θ) \cos (θ)$