In integration such as,
$$\int_{a}^{b} f(x) dx$$
It is said that that is the exact same as:
$$\int_{a}^{b} f(y) dy = \int_{a}^{b} f(\theta) d\theta = \int_{a}^{b} f(\alpha) d\alpha = \int_{a}^{b} f(\psi)d\psi$$
An the list goes on forever.
I cannot understand,
How is it justified to change the so-called 'dummy-variables'??
Thank you!
$$\int_{a}^{b} f(x) dx$$
It is said that that is the exact same as:
$$\int_{a}^{b} f(y) dy = \int_{a}^{b} f(\theta) d\theta = \int_{a}^{b} f(\alpha) d\alpha = \int_{a}^{b} f(\psi)d\psi$$
An the list goes on forever.
I cannot understand,
How is it justified to change the so-called 'dummy-variables'??
Thank you!