# Thread: vector calc questions

1. ## vector calc questions

I am studying for an exam and I am hoping that someone can clarify a couple of things:

If I have a airplane with vector of 304 i and negative 35 j (since it is traveling east and slightly south) when I compute the ground speed do I use

square root of 304^2 + 35^2 or would I use square root of 304^2 minus 35^2 since the airplane's direction is south not north. I am thinking that the ground does not care if we are going north or south but I am confused!!!!!!

I am given three points (0,0,0), (1,1,2) and (2,3,-1) and asked to find the area of the triangle with these vertices.

After a little thought, I chose to get two displacement vectors and then figured out their cross product. Since this would be the area of a parallogram I divided it by two to get the area of what I hope is the triangle. Did I think long enough on this or am I way off???

Thanks to all you folks out there who help others!!!!!

2. Hi

The coordinates of the vector are (304,-35)
The modulus is $\sqrt{304^2+(-35)^2}=\sqrt{304^2+35^2}$

For the area of the triangle you are right (divide by 2)