Precalculus Examples

$\cos (- 45)$

Step 1

Apply the reference angle by finding the angle with equivalent trig values in the first quadrant.

$\cos (45)$

Step 2

The exact value of $\cos (45)$ is $\frac{\sqrt{2}}{2}$ .

$\frac{\sqrt{2}}{2}$

Step 3

The result can be shown in multiple forms.

Exact Form:

$\frac{\sqrt{2}}{2}$

Decimal Form:

$0.70710678 \dots$