Step-by-step explanation:
[tex]\frac{( \csc x+1)( \csc x-1)}{ \csc ^2x} = \frac{ { \csc }^{2} x - 1}{ \csc^{2} x} \\ = 1 - \sin^{2} x = \cos^{2} x \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: [/tex]
b. Since csc theta = 1/sin theta, we can multiply both sides by sin theta and you will end up with
[tex] \cos^{2} \theta + \sin^{2} \theta = 1[/tex]
which is an identity.
