- #26

- 146

- 1

Simply because f(x) = g(u).

Hi,

Ok, so let us summarize.

(1)The domain of g(u) is the range of u = sin(x) + cos(x) which is [itex]-√2 ≤ u ≤ √2[/itex]

(2) The range of f(x) is the range of g(u)

You still cant treat "u" as an independent variable, you

**must apply the chain rule**. Just as you cant do this.

Find the derivative of [itex]f(x) = (2x^2 + 3x)^2[/itex]

Suppose you let u = 2x^2 + 3x then

[itex]f(x) = u^2 → f'(x) = 2u = 4x^2 + 6x[/itex]

**wrong**