Solution:
Given:
cot 35° cot 40° cot 45° cot 50° cot 55°
Concept used:
cot 45° = 1
tan θ × cot θ = 1
tan A = cot B, if A + B = 90°
Calculation:
cot 35° cot 40° cot 45° cot 50° cot 55°
⇒ cot 35° cot 40° cot 45° tan 40° tan 35°
⇒ cot 35° tan 35° cot 40° tan 40° cot 45°
⇒ cot 45° = 1
∴ The correct answer is 1.
