Pearsons corelation coefficient is defined as follows
$$ r_{x,y} =\frac {\sum (x_i -\bar X)(y_i - \bar Y)}{\sqrt{\sum(x_i-\bar X)^2} \sqrt{\sum(y_i-\bar Y)^2}} $$.
Now, maximum magnitude of a correlation coefficient is known to be $1$; which is possible only if
$$Numarator = denominator$$,
$$or, {\sum (x_i -\bar X)(y_i - \bar Y)}={\sqrt{\sum(x_i-\bar X)^2} \sqrt{\sum(y_i-\bar Y)^2}} ... (1) $$;
Now; if the dataset is perfectly corelated, then how or why the relation $... (1)$ works? or in other words, the denominator or numarator becomes equal?
Samely the alternate equation,
$$r_{xy}= \frac {n\sum X_iY_i- (\sum x_i)(\sum y_i)} {\sqrt{n\sum x_i^2 -(\sum x_i)^2} \sqrt{n\sum y_i^2-(\sum y_i)^2}}$$
now, the coefficient of correlation will be =1 only if
$$numerator=denominator$$
$$or,{n\sum X_iY_i- (\sum x_i)(\sum y_i)} = {\sqrt{n\sum x_i^2 -(\sum x_i)^2} \sqrt{n\sum y_i^2-(\sum y_i)^2}} ... (2) $$
If the dataset is perfectly correlated ; then how to tell relation $... (2)$ will work?
So in brief my question is ....
I am looking for necessarily intuitive explanation of what these mathematical terms mean; such as it is quite clear that ${\sum (x_i -\bar X)(y_i - \bar Y)}$ is a sum of areas made by the data points which comes from covariance. But why this exact same area will be cancelled out by the denominator, that I could not understand by any way.
What I tried already: