for me it is always continuous because theres the +1 in the denominator, however the back of my book says that the answer is all x except npi/2

x

^{2}+1 is never 0 if x is real. However, tan x = sinx/cosx is undefined when x = ±π/2, ±3π/2, ...So, the domain = {x l x ≠ ±π/2, ±3π/2, ...}

= {x l x ≠ nπ/2, where n is an odd integer}

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