Secant of Right Angle
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Theorem
- $\sec 90 \degrees = \sec \dfrac \pi 2$ is undefined
where $\sec$ denotes secant.
Proof
From Secant is Reciprocal of Cosine:
- $\sec \theta = \dfrac 1 {\cos \theta}$
From Cosine of Right Angle:
- $\cos \dfrac \pi 2 = 0$
Thus $\sec \theta$ is undefined at this value.
$\blacksquare$
Also see
- Sine of Right Angle
- Cosine of Right Angle
- Tangent of Right Angle
- Cotangent of Right Angle
- Cosecant of Right 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