How many solutions does the equation tan(2x) = tan(6x) have in the open interval (0, 3*pi)?
4
5
6
7
Correct answer: 7
Solution
From tan(2x) = tan(6x), we get 4x = n*pi so x = n*pi/4. We must exclude values where either tan(2x) or tan(6x) is undefined, then count valid x in (0, 3*pi).