Persamaan garis singgung pada kurva y=tanx di titik (phi/4,1)

y = tan x
   = sin x/ cos x

u = sin x , u' = cos x
v = cos x, v' = - sin x

y' = u'v - v'u / v²
   = cos x cos x - (-sin x) sin x / cos²x
   = (cos²x + sin²x) / cos²x
   =  1/ cos² x
   = sec²x 

m = y'
    = sec² x --> x = π/4
    = sec² π/4
    = (2/ √2)²
    = 2

pers garis singgung :
y- b = m (x-a)
y - 1 = 2 (x- π/4)
   y = 2x - π/2 + 1
  2y = 4x-π+2

4x-2y - π+2 = 0