Trigonometry Examples

$\cos (- \frac{π}{5})$

Step 1

Add full rotations of $2 π$ until the angle is greater than or equal to $0$ and less than $2 π$ .

$\cos (\frac{9 π}{5})$

Step 2

The result can be shown in multiple forms.

Exact Form:

$\cos (\frac{9 π}{5})$

Decimal Form:

$0.80901699 \dots$