Hence, the answer is:
[tex]\cot O=\dfrac{1}{\dfrac{-3}{8}}[/tex] or [tex]\cot 0=\dfrac{-8}{3}[/tex]
We know that the tangent trignometric function and the cotangent trignometric function is given by:
[tex]\tan x=\dfrac{1}{\cot x}[/tex]
i.e. the tangent function and the cotangent function are inverse of each other.
We are given tangent of an angle O as:
[tex]\tan 0=\dfrac{-3}{8}[/tex]
Hence, we have:
[tex]\cot O=\dfrac{1}{\tan O}\\\\i.e.\\\\\cot O=\dfrac{1}{\dfrac{-3}{8}}\\\\i.e.\\\\\cot O=\dfrac{8}{-3}\\\\i.e.\\\\\cot 0=\dfrac{-8}{3}[/tex]