#### notes

Sometimes the relation between two variables is neither explicit nor implicit, but some link of a third variable with each of the two variables, separately, establishes a relation between the first two variables. In such a situation, we say that the relation between them is expressed via a third variable. The third variable is called the parameter. More precisely, a relation expressed between two variables x and y in the form x = f(t), y = g(t) is said to be parametric form with t as a parameter.

In order to find derivative of function in such form, we have by chain rule.

`(dy)/(dt) = (dy)/(dx) . (dx)/(dt)`

or `(dy)/(dx)` = `(((dy)/(dt))/((dx)/(dt)))` `("whenever" (dx)/(dt) ≠ 0)`

Thus

`(dy)/(dx) = (g'(t))/(f'(t)) (as (dy)/(dt) = g'(t) and (dx)/(dt) = f'(t))` [provided f'(t) ≠ 0]

Video link : https://youtu.be/UEB6oqOQu1Q