How to Multiply Vectors?

How can I do this?

touch_start(integer total_number)
{

vector vecOne = <10, 5, 10>;
vector vecTwo = <5, 5, 5>;
vector vecThree = vecOne * vecTwo;

llSay(0, (string)vecThree);
}

You have two ways. The way you do it it is a DOT product and produces a float:
float f = vecOne * vecTwo;
The other product is a CROSS product and results in a vector perpendicular to both vectors in the argument:
vector vecThree = vecOne % vecTwo;

if you are expecting a result of <50, 25, 50> you'll need to multipl each element separately....

vector vecOne = <10, 5, 10>;
vector vecTwo = <5, 5, 5>;
vector vecThree = < vecOne.x * vecTwo.x, vecOne.y * vecTwo.y, vecOne.z * vecTwo.z >;

alternatively, if you know all the elements in one of the vectors are the same, you can do this

vector vecOne = <10, 5, 10>;
float fltTwo = 5.0;
vector vecThree = vecOne * fltTwo;

There's a big difference between vector multiplication (dot product or cross product), which Dora was describing, and scalar multiplication, which is what Void was describing. The OP better be sure that he knows which one he wants to do.

yup, and many expect the latter to occur with the former operator...

out of curiousity, would my first example actually be considered scalar? I'd think so, just with a variable magnitude, versus a universal one... but I'm not sure... calc was so long ago.

ps is it just me or are operators and precedence (my two original post excepted) coming up a lot more recently?

I understand what a dot product is, but could someone tell me why it's usful? I know it's the same in Matrix multiplcation, but I never really understand why it's useful?

The dot product of two vectors a and b is == |a| *|b| *cos Theta, where |a| and |b| denote the length of a and b and Theta is the angle between them. Among other things, this means that given two vectors, the angle between them can be found by rearranging this to get

Theta = arccos (( a . b)/(|a| *|b|)) .

Kind of a useful function.

also useful if you want to do matrix operations using vectors to store the lists instead of storing all those variables separately and then doing it all long hand... makes solving equations in 2 coefficients a heck of a lot faster =)

The dot product is useful in many ways. In relation to SL i is useful to find out if two vectors are perpendicular, they are if the dot product equals zero. Do two vectors point in the same direction? They do if the dot product of the normalized vectors equals one. If the dot product of the normalized vectors equals minus one, the two vectors point in opposite directions. For more math and more uses take a look at this site:
http://en.wikipedia.org/wiki/Dot_product