Tangent of Straight Angle

Theorem

 * $\tan 180^\circ = \tan \pi = 0$

where $\tan$ denotes tangent.

Also see

 * Sine of Straight Angle
 * Cosine of Straight Angle
 * Cotangent of Straight Angle
 * Secant of Straight Angle
 * Cosecant of Straight Angle