Let tan (15°) = tan(45°-30°)

We know that

We now

And

So, 3 tan (x - 15^o) = tan (x + 15^o) can be written as follows

(3 tan x – 3tan15)(1-tan x × tan15) = (1+tan x × tan15)(tan x + tan15)

3 tan x – 3 tan15-3 tan²x tan(15-3) tan x tan²15 = tan x + tan15 + tan²x tan15 + tan x tan²15

Solving the equation,

And putting

We get tan x - 1 = 0

Therefore, tan x =1

So, x=45°

Or