Alright, lets get started.
The answer Sandra got is correct that is zero but there are some mistakes she made while writing steps.
[tex] 2 cot(\frac{-9\pi}{2}) = 2 cot(\frac{9\pi}{2}) [/tex] Incorrect step
Because as per even/odd identity,
Cot (-Θ) = - cot (Θ)
Hence
[tex] 2 cot (\frac{-9\pi}{2}) = - 2 cot (\frac{9\pi}{2}) [/tex]
Now,
It could be written as
[tex] -2 cot (\frac{9\pi}{2}) = -2 cot (\frac{\pi}{2}) [/tex]
[tex] -2 * 0 [/tex]
0
Hence the answer is 0. : Answer
Hope it will help :)
