Chain rule

The rule in Calculus whereby:

df/dx = (df/du) * (du/dx)

or:

f '(x) = f '(u) * u '(x).

Note: a dash sign next to a letter indicates that the differential of that function is being reffered to. for any function f defined in terms of u, and any function u defined in terms of x.

For example:

• f(x) = 25x³sin(x)

• Call 25x³ function u

• Call sin(x) function v

• df/dx therefore equals: f'(x) = u'v + uv'

• Which equals: f'(x) = 75x²sin(x) + 25x³cos(x)