Which expression is equivalent to cos^2x +cot^2x +sin^2x?

a) 2 csc^2x
b) tan^2x
c) cot^2x
d) csc^2x

See the cos^2x +sin^2x in your cos^2x +cot^2x +sin^2x?

That equals to 1

Then, 1+ cot^2x = ?

You should know that 1+ cot^2x = cosec^2x