Question

prove that tan 10 tan 25 tan 45 tan 60 tan 80 = 1​

Answer 1

Answer:

tan10=tan(90-80)=cot80

tan25 = tan(90 - 65) = cot65

tan45 = 1

tan 10 tan 25 tan 45 tan 65 tan 80         (note tan60 is supposed to be tan65)

cot80*cot65*1*tan65*tan80

we know tanx*cotx=1

so,

tan 10 tan 25 tan 45 tan 65 tan 80=1