Question

Fill in the blank:
___________$-{\cot }^2\theta =1$

Answer 1

From the trigonomtric identity:

$1+{\cot }^2\theta ={\csc }^2\theta$

$\Rightarrow {\csc }^2\theta -{\cot }^2\theta =1$

Hence the required answer is ${\csc }^2\theta$.