Trigonometry Examples

$3 \cos (x) \cos (2 x)$

Step 1

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

$3 \cos (x) (2 \cos^{2} (x) - 1)$

Step 2

Apply the distributive property.

$3 \cos (x) (2 \cos^{2} (x)) + 3 \cos (x) \cdot - 1$

Step 3

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

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Step 3.1

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

$3 (\cos^{2} (x) \cos (x)) \cdot 2 + 3 \cos (x) \cdot - 1$

Step 3.2

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

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Step 3.2.1

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

$3 (\cos^{2} (x) \cos^{1} (x)) \cdot 2 + 3 \cos (x) \cdot - 1$

Step 3.2.2

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

$3 {\cos (x)}^{2 + 1} \cdot 2 + 3 \cos (x) \cdot - 1$

Step 3.3

Add $2$ and $1$ .

$3 \cos^{3} (x) \cdot 2 + 3 \cos (x) \cdot - 1$

Step 4

Multiply $- 1$ by $3$ .

$3 \cos^{3} (x) \cdot 2 - 3 \cos (x)$

Step 5

Multiply $2$ by $3$ .

$6 \cos^{3} (x) - 3 \cos (x)$