If x < 0, y < 0 such that xy = 1, then write the value of tan-1 x + tan-1 y

If x < 0, y < 0 such that xy = 1, then write the value of $\tan^{- 1} x + \tan^{- 1} y$

Matching exercise

Match the items on the right to the items on the left.

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