Answer
Write $\tan87^\circ$ in terms of the cofunction of the complementary angle:
$$\cot3^\circ$$
Work Step by Step
$$\tan87^\circ$$
Cotangent is the cofunction of tangent. That means the question asks to write $\tan87^\circ$ in terms of cotangent and an angle. In other words, what is $\theta$ with which
$$\cot\theta=\tan87^\circ\hspace{1cm}(1)$$
According to Cofunction Identity: $\cot\theta=\tan(90^\circ-\theta)$
Apply this to the equation $(1)$:
$$\tan(90^\circ-\theta)=\tan87^\circ$$
$$90^\circ-\theta=87^\circ$$
$$\theta=90^\circ-87^\circ=3^\circ$$
Therefore $\cot3^\circ$ is the answer.
