Secant of Straight Angle
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Theorem
- $\sec 180 \degrees = \sec \pi = -1$
where $\sec$ denotes secant.
Proof
\(\ds \sec 180 \degrees\) | \(=\) | \(\ds \map \sec {90 \degrees + 90 \degrees}\) | ||||||||||||
\(\ds \) | \(=\) | \(\ds -\csc 90 \degrees\) | Secant of Angle plus Right Angle | |||||||||||
\(\ds \) | \(=\) | \(\ds -1\) | Cosecant of Right Angle |
$\blacksquare$
Also see
- Sine of Straight Angle
- Cosine of Straight Angle
- Tangent of Straight Angle
- Cotangent of Straight Angle
- Cosecant of Straight Angle
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