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

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

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

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

Prove that: (a) tan 20^(@)tan40^(@)tan60^(@)tan 80^(@)=3 (b) tan9^(@)-tan27^(@)-tan63^(@)+tan81^(@)=4

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

Prove that: tan10^(@) tan20^(@)tan70^(@)tan80^(@)=1

Prove that : tan 70^(@) = tan 20^(@) + 2 tan 50^(@)

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