To solve the trigonometric expression we proceed as follows;
7(tan x)^3-21tanx=0
this can be written as:
7(tan x)^3=21tanx
dividing through by 7 we get:
(tan x)^3=tan x
dividing through by tan x we get:
(tanx)^1=1
hence;
tan x=+\-1
when tan x=1
x=45
when tan x=-1
x=-45
Given that our answer should be at the interval [0,2π] the answer:
45=45/180=1/4π
