The cgi calculator can handle expressions as
Decimal numbers multiplication  1.4*2.2
Division    2/3
Addision   5+0
Substraction 4-2
Paranthesis (5-4)/(3-1)
Bionomial 6:2
Factorial  5!

Random number between 0 and 1 - rand
sinus in radians - sin(1)
inverse sinus - asin(1)
Interger part - int(1.555 )
sum of integer in a range - sum(1,3)
The factorial is the product of all natrual numbers up to that number.
 For instace 4! = 4*3*2*1
0! is defined as 1

It is usefull to calculate the number of combinations is possible. For instace how
many different ways can 6 people sit at a table.
The first person has 6 chairs to choose from the second has 5, the third has 4 ...
 
Bionomial coefficent is calculated as  n!/ k!(n-k)!
In this calculator I use notaion n:k
It's usefull to how many combinations without order it's i a selection as a partial set.
For instance to many differnet teams of 5 can You pick from  8  8:5 = 56