Cotangent of 210 Degrees
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Theorem
- $\cot 210^\circ = \cot \dfrac {7 \pi} 6 = \sqrt 3$
where $\cot$ denotes cotangent.
Proof
\(\ds \cot 210^\circ\) | \(=\) | \(\ds \cot \left({360^\circ - 150^\circ}\right)\) | ||||||||||||
\(\ds \) | \(=\) | \(\ds -\cot 150^\circ\) | Cotangent of Conjugate Angle | |||||||||||
\(\ds \) | \(=\) | \(\ds \sqrt 3\) | Cotangent of 150 Degrees |
$\blacksquare$
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