Which expression is equivalent to sec2xcot2x?

The basic rule of cos is

cos x = 1 / sec x

so

sec 2x = 1 / cos 2x

cot 2x = 1 / tan 2x

tan 2x = sin 2x / cos 2x

so

cot 2x = cos 2x / sin 2x

therefore

sec2x cot2x

(1/cos2x) * (cos2x / sin2x)

1 / sin 2x

but sin 2x = 1 / cosec 2x

so the answer is cosec 2x