I'll assume those are squares. We know D is an identity:
[tex]\sin^2 x + \cos ^2 x = 1[/tex]
Dividing through by [tex]\sin ^2 x[/tex]
[tex]1 + \cot^2 x = \csc^2 x[/tex]
That's A.
Dividing the original through by [tex]\cos ^2 x[/tex]
[tex]\tan^2 x + 1 = \sec^2 x[/tex]
Not quite B, wrong sign on tangent.
C has the wrong sign on cosine squared as well.
Identities: A & D
