Question

the value of tan20°.tan40°.tan80°

Answer 1

add tan 60 to make things easier

Answer 2

then also wt is the use of it

Answer 3

woops!! looks like you can't use reflection formula

Answer 4

by "add" i think @experimentX means "multiply by"

Answer 5

lol .. yeah sorry.

Answer 6

just being picky
we knew what you meant

Answer 7

\[ \tan 20 \tan (60 - 20 ) \tan(60 + 20) = \tan 20 \left( \frac{\tan^2 60 - \tan^ 2 20 }{1 - \tan ^2 20 \tan ^2 60 }\right) \]
We also know that
\[ \tan (3*20) = \tan 60 \]
find the value of tan(20) and put is there

Answer 8

i got itt....

Answer 9

there is easier method
write it up as.

sin(20) sin(40) sin(80)
-------------------
cos(20) cos(40) cos(80)

then
\[\frac{\sin 20 \sin(60 - 20)\sin(60 + 20)}{\cos 20 \cos(60 - 20)\cos(60 + 20)}\]
after slight manipulation the numerator should turn to sin(3*20) and denominator should turn into cos(3*20) where you get tan(60) which is your value.1