What is the slope of this curve

I'm trying to find the slope of this curve.

SQRT(45^2-(X-45)^2)

If you could show the steps that was be awesome, thanks.

y = (45² - (x - 45)²)^½

Simplify the expression in the square root:

45² - (x - 45)² = 45² - (x² - 90x + 45²)
  = 90x - x²

so

y = (90x - x²)^½
dy/dx = ½(90x - x²)^(-½) (90 - 2x)
  = (45 - x)/√(90x - x²)