Precalculus Examples

$\cos (\frac{π}{2} - θ)$

Apply the difference of angles identity $\cos (x - y) = \cos (x) \cos (y) + \sin (x) \sin (y)$ .

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

Simplify terms.

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Simplify each term.

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

$0 \cos (θ) + \sin (\frac{π}{2}) \sin (θ)$

Multiply $0$ by $\cos (θ)$ .

$0 + \sin (\frac{π}{2}) \sin (θ)$

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

$0 + 1 \sin (θ)$

Multiply $\sin (θ)$ by $1$ .

$0 + \sin (θ)$

Add $0$ and $\sin (θ)$ .

$\sin (θ)$