Answer
$sec^{2}\theta $
Work Step by Step
$\sin ^{2}\left( -\theta \right) +\tan ^{2}\left( -\theta \right) +\cos ^{2}\left( -\theta \right) =1+\tan ^{2}\left( -\theta \right) =\dfrac {1}{\cos ^{2}\left( -\theta \right) }=\dfrac {1}{\cos ^{2}\theta }=sec^{2}\theta $
