câu 1
a.
tan(x - 15) = 5
suy ra x = 15 + arctan(5) + kpi
b.
tan(2x + 1) + cotx = 0
suy ra tan(2x + 1) = - cotx
suy ra tan(2x + 1) = tan(x + pi/2)
suy ra 2x + 1 = x + pi/2
suy ra x = pi/2 - 1 + kpi

c.
tan(x^2 + 2x + 3) = tan(2)
suy ra x^2 + 2x + 3 = 2 + kpi
suy ra x^2 + 2x + 1 = kpi
suy ra (x + 1)^2 = kpi
suy ra x + 1 = ± √(kpi)
suy ra x = ± √(kpi) - 1
d.
cotx^2 = 1
suy ra cotx = 1 hoặc cotx = -1
suy ra x = pi/4 + kpi hoặc x = -pi/4 + kpi

e.
tan(2x + 25) = -1
suy ra 2x + 25 = - 45 + k.180
suy ra 2x = -70 + k.180
suy ra x = -35 + k.90
f.
tan(x/2 - pi/3) = - √(3)
suy ra x/2 - pi/3 = -pi/3 + kpi
suy ra x/2 = kpi
suy ra x = kpi/2