jika f(x) = √x²+1 maka f¹(x) =

f(x) = √(x²+1)
y = √(x²+1)
y² = x² + 1
y² - 1 = x²
x² = y² - 1
x = √(y²-1)
f¹(x) = √( x² - 1)

f'(x)=(x²+1)^1/2
      = 1/2(x²+1)^-1/2 . 2x
      = x(x²+1)^-1/2
      = 1/(x(√x²+1)