Evaluate `"cot"^(-1)1/9+"cot"^(-1)4/5+"cot"^(-1)1`

Explanation

To evaluate the expression \( \cot^{-1}\left(\frac{1}{9}\right) + \cot^{-1}\left(\frac{4}{5}\right) + \cot^{-1}(1) \), we can follow these steps:

### Step 1: Convert cotangent inverse to tangent inverse
We know that:
\[ \cot^{-1}(x) = \tan^{-1}\left(\frac{1}{x}\right) \]
Using this property, we can rewrite the expression:
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