Answer
$y^{\circ}$
$ \tan(90-y)^{\circ} = \cot y^{\circ}$
Work Step by Step
Using Cofunction Theorem-
$ \tan(90-y)^{\circ} = \cot y^{\circ}$
Reason-
tangent and cotangent are cofunctions and
$ (90-y)^{\circ} + y^{\circ} = 90^{\circ}$
i.e. $(90-y)^{\circ}$ and $ y^{\circ}$ are complementary angles.
