UPSC CDS I 2019 Math Paper

tan 89° = tan (90° – 1°) = cot 1°
Similarly, tan 88° = cot 2°, and so on
Therefore, the given expression:
= tan 1°.tan 2° .tan3°.....tan 44°.tan 45°.cot 44°. ...cot 3° cot2° cot 1°
= tan 45° = 1