Complete the following equation. \[ \tan ^{2} \theta-\sec ^{2} \theta= \]

Step 1 ：Given the equation \(\tan^{2}\theta - \sec^{2}\theta\)

Step 2 ：We know that \(\tan^{2}\theta\) is equal to \(\sec^{2}\theta - 1\)

Step 3 ：Substitute \(\tan^{2}\theta\) with \(\sec^{2}\theta - 1\) in the equation

Step 4 ：The equation becomes \(\sec^{2}\theta - 1 - \sec^{2}\theta\)

Step 5 ：Simplify the equation to get the final answer

Step 6 ：Final Answer: \(\boxed{-1}\)