- #1
bigplanet401
- 104
- 0
Homework Statement
Why does
[itex]
\int_a^b \, y \; dx
[/itex]
become
[itex]
\int_\alpha^\beta \, g(t) f^\prime(t) \; dt
[/itex]
if x = f(t) and y = g(t) and alpha <= t <= beta?
Homework Equations
Substitution rule?
The Attempt at a Solution
I'm not sure how y = y(x) in the integrand turns into g(t). Isn't y a function of x in the first expression? How do they go from y(x) to g(t)?