in comp. science , which part of the mathematics is important/use?

Answer 1

Statistics - and of course any math training your logical skills (i.e. algebra) will help your brain coping successfully with computer topics.

Answer 2

Depends on what you are going to do with it.
The majority of math done on the computer is simple algebra.

It has more to do with problem solving, if you can't do math usually you won't do well in comp. science, but it doesn't neccesarily mean you will ever use differential equations or trig in any piece of software you write.

Just learn how to think logically.

You are using a 32 bit system.
Lets say someone tells you to swap the first 16 bits and the second 16 bits on an array of 10 integers.

Well each integer is 32 bits on a 32 bits system.

int swap(){
int i, iarray[10];
for(i=0; i <= 9; i++){
iarray[i] = (iarray[i] >> 16) | (iarray[i] << 16);
}
}

This is a simple problem that took logical thinking to come up with.

Beyond that it's what you want to apply your programming skills on.

Answer 3

All of it, at some point, will probably come into play. On a daily basis, algorithms (even in Object Oriented designs!), logic, binary/octal/decimal/hexadecimal conversions, precedence rules and whatever math applies to the functions in the project you're doing at the time.