Trigonometry Examples

$\sqrt{7} \sin (x) + \sqrt{21} \cos (x) = ks i n (x + x)$

Step 1

Square both sides of the equation.

${(\sqrt{7} \sin (x) + \sqrt{21} \cos (x))}^{2} = {(ks i n (x + x))}^{2}$

Step 2

Simplify ${(\sqrt{7} \sin (x) + \sqrt{21} \cos (x))}^{2}$ .

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Step 2.1

Rewrite ${(\sqrt{7} \sin (x) + \sqrt{21} \cos (x))}^{2}$ as $(\sqrt{7} \sin (x) + \sqrt{21} \cos (x)) (\sqrt{7} \sin (x) + \sqrt{21} \cos (x))$ .

$(\sqrt{7} \sin (x) + \sqrt{21} \cos (x)) (\sqrt{7} \sin (x) + \sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.2

Expand $(\sqrt{7} \sin (x) + \sqrt{21} \cos (x)) (\sqrt{7} \sin (x) + \sqrt{21} \cos (x))$ using the FOIL Method.

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Step 2.2.1

Apply the distributive property.

$\sqrt{7} \sin (x) (\sqrt{7} \sin (x) + \sqrt{21} \cos (x)) + \sqrt{21} \cos (x) (\sqrt{7} \sin (x) + \sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.2.2

Apply the distributive property.

$\sqrt{7} \sin (x) (\sqrt{7} \sin (x)) + \sqrt{7} \sin (x) (\sqrt{21} \cos (x)) + \sqrt{21} \cos (x) (\sqrt{7} \sin (x) + \sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.2.3

Apply the distributive property.

$\sqrt{7} \sin (x) (\sqrt{7} \sin (x)) + \sqrt{7} \sin (x) (\sqrt{21} \cos (x)) + \sqrt{21} \cos (x) (\sqrt{7} \sin (x)) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3

Simplify and combine like terms.

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Step 2.3.1

Simplify each term.

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Step 2.3.1.1

Multiply $\sqrt{7} \sin (x) (\sqrt{7} \sin (x))$ .

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Step 2.3.1.1.1

Raise $\sqrt{7}$ to the power of $1$ .

${\sqrt{7}}^{1} \sqrt{7} \sin (x) \sin (x) + \sqrt{7} \sin (x) (\sqrt{21} \cos (x)) + \sqrt{21} \cos (x) (\sqrt{7} \sin (x)) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.1.2

Raise $\sqrt{7}$ to the power of $1$ .

${\sqrt{7}}^{1} {\sqrt{7}}^{1} \sin (x) \sin (x) + \sqrt{7} \sin (x) (\sqrt{21} \cos (x)) + \sqrt{21} \cos (x) (\sqrt{7} \sin (x)) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.1.3

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

${\sqrt{7}}^{1 + 1} \sin (x) \sin (x) + \sqrt{7} \sin (x) (\sqrt{21} \cos (x)) + \sqrt{21} \cos (x) (\sqrt{7} \sin (x)) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.1.4

Add $1$ and $1$ .

${\sqrt{7}}^{2} \sin (x) \sin (x) + \sqrt{7} \sin (x) (\sqrt{21} \cos (x)) + \sqrt{21} \cos (x) (\sqrt{7} \sin (x)) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.1.5

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

${\sqrt{7}}^{2} (\sin^{1} (x) \sin (x)) + \sqrt{7} \sin (x) (\sqrt{21} \cos (x)) + \sqrt{21} \cos (x) (\sqrt{7} \sin (x)) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.1.6

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

${\sqrt{7}}^{2} (\sin^{1} (x) \sin^{1} (x)) + \sqrt{7} \sin (x) (\sqrt{21} \cos (x)) + \sqrt{21} \cos (x) (\sqrt{7} \sin (x)) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.1.7

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

${\sqrt{7}}^{2} {\sin (x)}^{1 + 1} + \sqrt{7} \sin (x) (\sqrt{21} \cos (x)) + \sqrt{21} \cos (x) (\sqrt{7} \sin (x)) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.1.8

Add $1$ and $1$ .

${\sqrt{7}}^{2} \sin^{2} (x) + \sqrt{7} \sin (x) (\sqrt{21} \cos (x)) + \sqrt{21} \cos (x) (\sqrt{7} \sin (x)) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.2

Rewrite ${\sqrt{7}}^{2}$ as $7$ .

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Step 2.3.1.2.1

Use $\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite $\sqrt{7}$ as $7^{\frac{1}{2}}$ .

${(7^{\frac{1}{2}})}^{2} \sin^{2} (x) + \sqrt{7} \sin (x) (\sqrt{21} \cos (x)) + \sqrt{21} \cos (x) (\sqrt{7} \sin (x)) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.2.2

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

$7^{\frac{1}{2} \cdot 2} \sin^{2} (x) + \sqrt{7} \sin (x) (\sqrt{21} \cos (x)) + \sqrt{21} \cos (x) (\sqrt{7} \sin (x)) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.2.3

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

$7^{\frac{2}{2}} \sin^{2} (x) + \sqrt{7} \sin (x) (\sqrt{21} \cos (x)) + \sqrt{21} \cos (x) (\sqrt{7} \sin (x)) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.2.4

Cancel the common factor of $2$ .

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Step 2.3.1.2.4.1

Cancel the common factor.

$7^{\frac{2}{2}} \sin^{2} (x) + \sqrt{7} \sin (x) (\sqrt{21} \cos (x)) + \sqrt{21} \cos (x) (\sqrt{7} \sin (x)) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.2.4.2

Rewrite the expression.

$7^{1} \sin^{2} (x) + \sqrt{7} \sin (x) (\sqrt{21} \cos (x)) + \sqrt{21} \cos (x) (\sqrt{7} \sin (x)) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.2.5

Evaluate the exponent.

$7 \sin^{2} (x) + \sqrt{7} \sin (x) (\sqrt{21} \cos (x)) + \sqrt{21} \cos (x) (\sqrt{7} \sin (x)) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.3

Multiply $\sqrt{7} \sin (x) (\sqrt{21} \cos (x))$ .

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Step 2.3.1.3.1

Combine using the product rule for radicals.

$7 \sin^{2} (x) + \sqrt{21 \cdot 7} \sin (x) \cos (x) + \sqrt{21} \cos (x) (\sqrt{7} \sin (x)) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.3.2

Multiply $21$ by $7$ .

$7 \sin^{2} (x) + \sqrt{147} \sin (x) \cos (x) + \sqrt{21} \cos (x) (\sqrt{7} \sin (x)) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.4

Rewrite $147$ as $7^{2} \cdot 3$ .

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Step 2.3.1.4.1

Factor $49$ out of $147$ .

$7 \sin^{2} (x) + \sqrt{49 (3)} \sin (x) \cos (x) + \sqrt{21} \cos (x) (\sqrt{7} \sin (x)) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.4.2

Rewrite $49$ as $7^{2}$ .

$7 \sin^{2} (x) + \sqrt{7^{2} \cdot 3} \sin (x) \cos (x) + \sqrt{21} \cos (x) (\sqrt{7} \sin (x)) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.5

Pull terms out from under the radical.

$7 \sin^{2} (x) + 7 \sqrt{3} \sin (x) \cos (x) + \sqrt{21} \cos (x) (\sqrt{7} \sin (x)) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.6

Multiply $\sqrt{21} \cos (x) (\sqrt{7} \sin (x))$ .

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Step 2.3.1.6.1

Combine using the product rule for radicals.

$7 \sin^{2} (x) + 7 \sqrt{3} \sin (x) \cos (x) + \sqrt{7 \cdot 21} \cos (x) \sin (x) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.6.2

Multiply $7$ by $21$ .

$7 \sin^{2} (x) + 7 \sqrt{3} \sin (x) \cos (x) + \sqrt{147} \cos (x) \sin (x) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.7

Rewrite $147$ as $7^{2} \cdot 3$ .

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Step 2.3.1.7.1

Factor $49$ out of $147$ .

$7 \sin^{2} (x) + 7 \sqrt{3} \sin (x) \cos (x) + \sqrt{49 (3)} \cos (x) \sin (x) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.7.2

Rewrite $49$ as $7^{2}$ .

$7 \sin^{2} (x) + 7 \sqrt{3} \sin (x) \cos (x) + \sqrt{7^{2} \cdot 3} \cos (x) \sin (x) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.8

Pull terms out from under the radical.

$7 \sin^{2} (x) + 7 \sqrt{3} \sin (x) \cos (x) + 7 \sqrt{3} \cos (x) \sin (x) + \sqrt{21} \cos (x) (\sqrt{21} \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.9

Multiply $\sqrt{21} \cos (x) (\sqrt{21} \cos (x))$ .

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Step 2.3.1.9.1

Raise $\sqrt{21}$ to the power of $1$ .

$7 \sin^{2} (x) + 7 \sqrt{3} \sin (x) \cos (x) + 7 \sqrt{3} \cos (x) \sin (x) + {\sqrt{21}}^{1} \sqrt{21} \cos (x) \cos (x) = {(ks i n (x + x))}^{2}$

Step 2.3.1.9.2

Raise $\sqrt{21}$ to the power of $1$ .

$7 \sin^{2} (x) + 7 \sqrt{3} \sin (x) \cos (x) + 7 \sqrt{3} \cos (x) \sin (x) + {\sqrt{21}}^{1} {\sqrt{21}}^{1} \cos (x) \cos (x) = {(ks i n (x + x))}^{2}$

Step 2.3.1.9.3

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

$7 \sin^{2} (x) + 7 \sqrt{3} \sin (x) \cos (x) + 7 \sqrt{3} \cos (x) \sin (x) + {\sqrt{21}}^{1 + 1} \cos (x) \cos (x) = {(ks i n (x + x))}^{2}$

Step 2.3.1.9.4

Add $1$ and $1$ .

$7 \sin^{2} (x) + 7 \sqrt{3} \sin (x) \cos (x) + 7 \sqrt{3} \cos (x) \sin (x) + {\sqrt{21}}^{2} \cos (x) \cos (x) = {(ks i n (x + x))}^{2}$

Step 2.3.1.9.5

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

$7 \sin^{2} (x) + 7 \sqrt{3} \sin (x) \cos (x) + 7 \sqrt{3} \cos (x) \sin (x) + {\sqrt{21}}^{2} (\cos^{1} (x) \cos (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.9.6

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

$7 \sin^{2} (x) + 7 \sqrt{3} \sin (x) \cos (x) + 7 \sqrt{3} \cos (x) \sin (x) + {\sqrt{21}}^{2} (\cos^{1} (x) \cos^{1} (x)) = {(ks i n (x + x))}^{2}$

Step 2.3.1.9.7

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

$7 \sin^{2} (x) + 7 \sqrt{3} \sin (x) \cos (x) + 7 \sqrt{3} \cos (x) \sin (x) + {\sqrt{21}}^{2} {\cos (x)}^{1 + 1} = {(ks i n (x + x))}^{2}$

Step 2.3.1.9.8

Add $1$ and $1$ .

$7 \sin^{2} (x) + 7 \sqrt{3} \sin (x) \cos (x) + 7 \sqrt{3} \cos (x) \sin (x) + {\sqrt{21}}^{2} \cos^{2} (x) = {(ks i n (x + x))}^{2}$

Step 2.3.1.10

Rewrite ${\sqrt{21}}^{2}$ as $21$ .

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Step 2.3.1.10.1

Use $\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite $\sqrt{21}$ as $21^{\frac{1}{2}}$ .

$7 \sin^{2} (x) + 7 \sqrt{3} \sin (x) \cos (x) + 7 \sqrt{3} \cos (x) \sin (x) + {(21^{\frac{1}{2}})}^{2} \cos^{2} (x) = {(ks i n (x + x))}^{2}$

Step 2.3.1.10.2

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

$7 \sin^{2} (x) + 7 \sqrt{3} \sin (x) \cos (x) + 7 \sqrt{3} \cos (x) \sin (x) + 21^{\frac{1}{2} \cdot 2} \cos^{2} (x) = {(ks i n (x + x))}^{2}$

Step 2.3.1.10.3

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

$7 \sin^{2} (x) + 7 \sqrt{3} \sin (x) \cos (x) + 7 \sqrt{3} \cos (x) \sin (x) + 21^{\frac{2}{2}} \cos^{2} (x) = {(ks i n (x + x))}^{2}$

Step 2.3.1.10.4

Cancel the common factor of $2$ .

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Step 2.3.1.10.4.1

Cancel the common factor.

$7 \sin^{2} (x) + 7 \sqrt{3} \sin (x) \cos (x) + 7 \sqrt{3} \cos (x) \sin (x) + 21^{\frac{2}{2}} \cos^{2} (x) = {(ks i n (x + x))}^{2}$

Step 2.3.1.10.4.2

Rewrite the expression.

$7 \sin^{2} (x) + 7 \sqrt{3} \sin (x) \cos (x) + 7 \sqrt{3} \cos (x) \sin (x) + 21^{1} \cos^{2} (x) = {(ks i n (x + x))}^{2}$

Step 2.3.1.10.5

Evaluate the exponent.

$7 \sin^{2} (x) + 7 \sqrt{3} \sin (x) \cos (x) + 7 \sqrt{3} \cos (x) \sin (x) + 21 \cos^{2} (x) = {(ks i n (x + x))}^{2}$

Step 2.3.2

Reorder the factors of $7 \sqrt{3} \sin (x) \cos (x)$ .

$7 \sin^{2} (x) + 7 \sqrt{3} \cos (x) \sin (x) + 7 \sqrt{3} \cos (x) \sin (x) + 21 \cos^{2} (x) = {(ks i n (x + x))}^{2}$

Step 2.3.3

Add $7 \sqrt{3} \cos (x) \sin (x)$ and $7 \sqrt{3} \cos (x) \sin (x)$ .

$7 \sin^{2} (x) + 14 \sqrt{3} \cos (x) \sin (x) + 21 \cos^{2} (x) = {(ks i n (x + x))}^{2}$

Step 3

Simplify ${(ks i n (x + x))}^{2}$ .

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Step 3.1

Add $x$ and $x$ .

$7 \sin^{2} (x) + 14 \sqrt{3} \cos (x) \sin (x) + 21 \cos^{2} (x) = {(ks i n (2 x))}^{2}$

Step 3.2

Rewrite using the commutative property of multiplication.

$7 \sin^{2} (x) + 14 \sqrt{3} \cos (x) \sin (x) + 21 \cos^{2} (x) = {(2 (ks i) n x)}^{2}$

Step 3.3

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

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Step 3.3.1

Apply the product rule to $2 (ks i) n x$ .

$7 \sin^{2} (x) + 14 \sqrt{3} \cos (x) \sin (x) + 21 \cos^{2} (x) = {(2 (ks i) n)}^{2} x^{2}$

Step 3.3.2

Apply the product rule to $2 (ks i) n$ .

$7 \sin^{2} (x) + 14 \sqrt{3} \cos (x) \sin (x) + 21 \cos^{2} (x) = {(2 (ks i))}^{2} n^{2} x^{2}$

Step 3.3.3

Apply the product rule to $2 (ks i)$ .

$7 \sin^{2} (x) + 14 \sqrt{3} \cos (x) \sin (x) + 21 \cos^{2} (x) = 2^{2} {(ks i)}^{2} n^{2} x^{2}$

Step 3.4

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

$7 \sin^{2} (x) + 14 \sqrt{3} \cos (x) \sin (x) + 21 \cos^{2} (x) = 4 {(ks i)}^{2} n^{2} x^{2}$

Step 4

Subtract $4 {(ks i)}^{2} n^{2} x^{2}$ from both sides of the equation.

$7 \sin^{2} (x) + 14 \sqrt{3} \cos (x) \sin (x) + 21 \cos^{2} (x) - 4 {(ks i)}^{2} n^{2} x^{2} = 0$

Step 5

Replace the $7 \sin^{2} (x)$ with $7 (1 - \cos^{2} (x))$ based on the $\sin^{2} (x) + \cos^{2} (x) = 1$ identity.

$7 (1 - \cos^{2} (x)) + 14 \sqrt{3} \cos (x) \sin (x) + 21 \cos^{2} (x) - 4 {(ks i)}^{2} n^{2} x^{2} = 0$

Step 6

Simplify each term.

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Step 6.1

Apply the distributive property.

$7 \cdot 1 + 7 (- \cos^{2} (x)) + 14 \sqrt{3} \cos (x) \sin (x) + 21 \cos^{2} (x) - 4 {(ks i)}^{2} n^{2} x^{2} = 0$

Step 6.2

Multiply $7$ by $1$ .

$7 + 7 (- \cos^{2} (x)) + 14 \sqrt{3} \cos (x) \sin (x) + 21 \cos^{2} (x) - 4 {(ks i)}^{2} n^{2} x^{2} = 0$

Step 6.3

Multiply $- 1$ by $7$ .

$7 - 7 \cos^{2} (x) + 14 \sqrt{3} \cos (x) \sin (x) + 21 \cos^{2} (x) - 4 {(ks i)}^{2} n^{2} x^{2} = 0$

Step 7

Add $- 7 \cos^{2} (x)$ and $21 \cos^{2} (x)$ .

$7 + 14 \cos^{2} (x) + 14 \sqrt{3} \cos (x) \sin (x) - 4 {(ks i)}^{2} n^{2} x^{2} = 0$

Step 8

Simplify $7 + 14 \cos^{2} (x) + 14 \sqrt{3} \cos (x) \sin (x) - 4 {(ks i)}^{2} n^{2} x^{2} = 0$ .

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Step 8.1

Simplify each term.

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Step 8.1.1

Apply the product rule to $ks i$ .

$7 + 14 \cos^{2} (x) + 14 \sqrt{3} \cos (x) \sin (x) - 4 ({ks}^{2} i^{2}) n^{2} x^{2} = 0$

Step 8.1.2

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

$7 + 14 \cos^{2} (x) + 14 \sqrt{3} \cos (x) \sin (x) - 4 ({ks}^{2} \cdot - 1) n^{2} x^{2} = 0$

Step 8.1.3

Move $- 1$ to the left of ${ks}^{2}$ .

$7 + 14 \cos^{2} (x) + 14 \sqrt{3} \cos (x) \sin (x) - 4 (- 1 {ks}^{2}) n^{2} x^{2} = 0$

Step 8.1.4

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

$7 + 14 \cos^{2} (x) + 14 \sqrt{3} \cos (x) \sin (x) - 4 (- {ks}^{2}) n^{2} x^{2} = 0$

Step 8.1.5

Multiply $- 1$ by $- 4$ .

$7 + 14 \cos^{2} (x) + 14 \sqrt{3} \cos (x) \sin (x) + 4 {ks}^{2} n^{2} x^{2} = 0$

Step 8.2

Reorder factors in $7 + 14 \cos^{2} (x) + 14 \sqrt{3} \cos (x) \sin (x) + 4 {ks}^{2} n^{2} x^{2} = 0$ .

$7 + 14 \cos^{2} (x) + 14 \sqrt{3} \cos (x) \sin (x) + 4 n^{2} x^{2} {ks}^{2} = 0$