11: You should get

Note that the zero in logarithm was specified as "positive zero". It had to be investigated, since ln(0) does not exist. How was the "positive" part deduced? For any n, arctan(n) < π/2, so the expression in logarithm is always positive and goes to zero, hence positive zero.

No trick for the resulting indeterminate ratio can be seen, so it is up to the standard procedure: Use the l'Hospital rule.

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