Question

What is the value of $\cot ( - 870^{\circ})$ ?

• A. $\sqrt{3}$
• B. $\frac{1}{\sqrt{3}}$
• C. $ - \sqrt{3}$
• D. $ - \frac{1}{\sqrt{3}}$

Answer 1

Answer: (A)

$\cot ( - 870^{\circ}) = - \cot ( 2 \times 360^{\circ} +150^{\circ})$
$= - \cot \, 150^{\circ} = - \cot (180^{\circ} - 30^{\circ})$
$= \cot \, 30^{\circ} = \sqrt{3}$.