cot(2x-3pi/4)=tan(x-pi/6)
<=> tan (pi/2 - 2x +3pi/4) = tan (x-pi/6) (áp dụng công thức tan (pi/2 - alpha) = cot alpha)
<=> tan (5pi/4 - 2x) = tan (x-pi/6)
<=> $\pi$ $\left \{ {{x - pi/6 ≠ pi/2 + k'pi} \atop {5pi/4 - 2x = x-pi/6 + kpi}} \right.$
<=> $\left \{ {{x ≠ 2pi/3 +k'pi} \atop {3x = 17pi/12 - kpi}} \right.$ $\left \{ {{x ≠ 2pi/3 +k'pi} \atop {x = 17pi/36 - kpi/3}} \right.$
<=> x = 17pi/36 - kpi/3
