First convert the angle measure from radians to degrees using the formula
[tex]\theta\cdot\frac{180}{\pi}[/tex]Were θ represents the angle of interest
So for this exercise the angle is pi, so:
[tex]\pi\cdot\frac{180}{\pi}=180[/tex]Now using the calculator you can determine tha tangent of negative 180º
tan(-180º)=0
So the tangent of negative pi should also be zero