Prove `tan 20^0 tan 30^0 tan 40^0 tan 80^0=1`

Prove that : tan 20^0 tan 40^0 tan 60^0 tan 80^0 =3

Prove that: t a n 20^0tan40^0tan60^0tan80^0=3

Prove that: tan20^0tan40^0tan80^0=tan60^0

Prove that tan20^0tan40^0tan80^0=tan60^0

Prove that: tan10^0tan15^0tan75^0tan80^0=1 tan1^0tan2^0tan3^0.....tan89^0=1 cos1^0cos2^0cos3^0.......cos180^0=0

Prove that tan70^0=2tan50^0+tan20^0

0 tan 2A=

Prove that: tan6^0tan42^0tan66^0tan78^0=1.

The value of (tan7 0^0-tan2 0^0)/(tan5 0^0)=

Without using trigonometric tables, evaluate each of the following: (-tanthetacot(90^0-theta)+secthetacos e c(90^0-theta)+sin^2 35^0+sin^2 55^0)/(tan10^0tan20^0tan30^0tan70^0tan80^0)