Prove that `tan20^0tan40^0tan60^0tan80^0`=3

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

The value of tan6^0tan42^0tan66^0tan78^0 is (a)1 (b) 1/2 (c) 1/4 (d) 1/8

Prove that tan70^(@)-tan20^(@)-2tan40^(@)=4tan10^(@) . (b) In a DeltaABC , if a=2sqrt3,b=2sqrt2andC=75^(@) find the other side and the angles.

Show that tan1^0tan2^0.....tan89^0=1

Prove that tan 70^(@)-tan 20^(@)-2 tan 40^(@)=4 tan 10^(@)

Prove that tan3A=(3tanA-tan^3 A)/(1-3tan^2 A)

Prove that (1+tan1^0)(1+tan2^0)......(1+tan45^0)=2^(23)dot

Prove that: cos 80^0+cos 40^0-cos 20^0=0

Find the value of the following: tan15^(@)tan30^(@)tan45^(@)tan60^(@)tan75^(@)

Prove that (tan^(2)2theta-tan^(2)theta)/(1-tan^(2)2thetatan^(2)theta)=tan 3 theta tan theta .