Giải phương trình: tan(x + π/3) - tan2x = 0; sin^2x + cos^2(2x) = 1; tan3x + cot(x + π /7) = 1

a. tan(x + π/3) - tan2x = 0
b. sin^2x + cos^2(2x) = 1
c. tan3x + cot (x +π /7) = 1
d. cot(2x - π/6 ) - cot4x = 0
e. tan(x + π/5) + tan 3x = 0
f. tan2x. tan (x + π/4) = 1