Cosecant of Straight Angle

Theorem

$\csc 180 \degrees = \csc \pi$ is undefined

where $\csc$ denotes cosecant.


Proof

From Cosecant is Reciprocal of Sine:

$\csc \theta = \dfrac 1 {\sin \theta}$

From Sine of Straight Angle:

$\sin \pi = 0$

Thus $\csc \theta$ is undefined at this value.

$\blacksquare$


Also see


Sources

  • 1968: Murray R. Spiegel: Mathematical Handbook of Formulas and Tables ... (previous) ... (next): $\S 5$: Trigonometric Functions: Exact Values for Trigonometric Functions of Various Angles
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