Consider the following for the next two (02) items that follow :

Let f(x) = sin[π²]x + cos[-π²]x where [.] is a greatest ‘integer function

What is $f\left(\frac{\pi}{4}\right)$ equal to ? 

If f(x) = x² + 2 and g(x) = 2x - 3, then what is (fog)(1) equal to ?

What is the range of the function f(x) = x + |x| if the domain is the set of real numbers ?  

What is $\displaystyle\sum_{x=1}^5$f(2x − 1) equal to ?