Answer
$1$
Work Step by Step
$sec^2\theta -\tan ^{2}\theta =\dfrac {1}{\cos ^{2}\theta }-\dfrac {\sin ^{2}\theta }{\cos ^{2}\theta }=\dfrac {1-\sin ^{2}\theta }{\cos ^{2}\theta }=\dfrac {\cos ^{2}\theta }{\cos ^{2}\theta }=1$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.