Trigonometry Examples

${(\sin (t) + \cos (t))}^{2} = 1 + \sin (2 t)$

Step 1

Start on the left side.

${(\sin (t) + \cos (t))}^{2}$

Step 2

Simplify the expression.

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Step 2.1

Rewrite ${(\sin (t) + \cos (t))}^{2}$ as $(\sin (t) + \cos (t)) (\sin (t) + \cos (t))$ .

$(\sin (t) + \cos (t)) (\sin (t) + \cos (t))$

Step 2.2

Expand $(\sin (t) + \cos (t)) (\sin (t) + \cos (t))$ using the FOIL Method.

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Step 2.2.1

Apply the distributive property.

$\sin (t) (\sin (t) + \cos (t)) + \cos (t) (\sin (t) + \cos (t))$

Step 2.2.2

Apply the distributive property.

$\sin (t) \sin (t) + \sin (t) \cos (t) + \cos (t) (\sin (t) + \cos (t))$

Step 2.2.3

Apply the distributive property.

$\sin (t) \sin (t) + \sin (t) \cos (t) + \cos (t) \sin (t) + \cos (t) \cos (t)$

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 $\sin (t) \sin (t)$ .

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Step 2.3.1.1.1

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

$\sin^{1} (t) \sin (t) + \sin (t) \cos (t) + \cos (t) \sin (t) + \cos (t) \cos (t)$

Step 2.3.1.1.2

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

$\sin^{1} (t) \sin^{1} (t) + \sin (t) \cos (t) + \cos (t) \sin (t) + \cos (t) \cos (t)$

Step 2.3.1.1.3

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

${\sin (t)}^{1 + 1} + \sin (t) \cos (t) + \cos (t) \sin (t) + \cos (t) \cos (t)$

Step 2.3.1.1.4

Add $1$ and $1$ .

$\sin^{2} (t) + \sin (t) \cos (t) + \cos (t) \sin (t) + \cos (t) \cos (t)$

Step 2.3.1.2

Multiply $\cos (t) \cos (t)$ .

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Step 2.3.1.2.1

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

$\sin^{2} (t) + \sin (t) \cos (t) + \cos (t) \sin (t) + \cos^{1} (t) \cos (t)$

Step 2.3.1.2.2

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

$\sin^{2} (t) + \sin (t) \cos (t) + \cos (t) \sin (t) + \cos^{1} (t) \cos^{1} (t)$

Step 2.3.1.2.3

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

$\sin^{2} (t) + \sin (t) \cos (t) + \cos (t) \sin (t) + {\cos (t)}^{1 + 1}$

Step 2.3.1.2.4

Add $1$ and $1$ .

$\sin^{2} (t) + \sin (t) \cos (t) + \cos (t) \sin (t) + \cos^{2} (t)$

Step 2.3.2

Reorder the factors of $\sin (t) \cos (t)$ .

$\sin^{2} (t) + \cos (t) \sin (t) + \cos (t) \sin (t) + \cos^{2} (t)$

Step 2.3.3

Add $\cos (t) \sin (t)$ and $\cos (t) \sin (t)$ .

$\sin^{2} (t) + 2 \cos (t) \sin (t) + \cos^{2} (t)$

Step 2.4

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

$\sin^{2} (t) + \cos^{2} (t) + 2 \cos (t) \sin (t)$

Step 2.5

Apply pythagorean identity.

$1 + 2 \cos (t) \sin (t)$

Step 2.6

Simplify each term.

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Step 2.6.1

Reorder $2 \cos (t)$ and $\sin (t)$ .

$1 + \sin (t) (2 \cos (t))$

Step 2.6.2

Reorder $\sin (t)$ and $2$ .

$1 + 2 \cdot \sin (t) \cos (t)$

Step 2.6.3

Apply the sine double-angle identity.

$1 + \sin (2 t)$

Step 3

Because the two sides have been shown to be equivalent, the equation is an identity.

${(\sin (t) + \cos (t))}^{2} = 1 + \sin (2 t)$ is an identity