Diffrentiation

y = (1+tanx) / (1-tan x)

tan 45 = 1,

Hence, we can write,

y = (tan 45 + tanx) / (1 - tan x tan 45)

= (tan (45+x))

dy/dx = [1/2(tan (45+x))] sec²(45+x)

= [1/2(tan (45+x))] [1 + tan²(45+x)]

Regards,

Team,

TopperLearning.