Precalculus Examples

$\sin (\frac{π}{2} + θ) = \cos (θ)$

Step 1

Start on the left side.

$\sin (\frac{π}{2} + θ)$

Step 2

Apply the sum of angles identity.

$\sin (\frac{π}{2}) \cos (θ) + \cos (\frac{π}{2}) \sin (θ)$

Step 3

Simplify the expression.

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Step 3.1

Simplify each term.

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Step 3.1.1

The exact value of $\sin (\frac{π}{2})$ is $1$ .

$1 \cos (θ) + \cos (\frac{π}{2}) \sin (θ)$

Step 3.1.2

Multiply $\cos (θ)$ by $1$ .

$\cos (θ) + \cos (\frac{π}{2}) \sin (θ)$

Step 3.1.3

The exact value of $\cos (\frac{π}{2})$ is $0$ .

$\cos (θ) + 0 \sin (θ)$

Step 3.1.4

Multiply $0$ by $\sin (θ)$ .

$\cos (θ) + 0$

Step 3.2

Add $\cos (θ)$ and $0$ .

$\cos (θ)$

Step 4

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

$\sin (\frac{π}{2} + θ) = \cos (θ)$ is an identity