Phi Π: Greetings. , welcome to my classroom, where i teach you all about summation and the value of all constants, like pi and tau, tau is just pi x 2, so if your looking to write it down on a formula. Write it like this.

π x 2 = n

Oh but for my formula, its like this.

For example, 7 x 5 x 9, write it like this.

$\prod_{k=1}^3 k = 7 \cdot 5 \cdot 9 = 315$

This is equivalent to multiplying the numbers together in the order they are written:

$7 \cdot 5 \cdot 9 = 315$