Question

tan10° tan75° tan75° tan80° = 1

Answer 1

first of all tan 7 5 degree is tan 15 degree
cot(90°-10°)× cot(90°-15°)×tan75°×tan80° =1
cot80° cot75° tan75° tan80° =1
since tan = cot = 1/tan
1/tan80°×1/tan75°×tan75°×tan80°=1
1=1 hence proved
I hope it works ,