# Calc III, Vector trouble, help would be great!

by mr_coffee
Tags: calc, trouble, vector
 P: 117 4. i'm not sure what you're looking for here. do you have coordinates for Q, S, P, and R? remember that a vector in $$R^3$$ is $$\vec{A} = \left( \begin{array}{cc} A_x \\ A_y\\ A_z \end{array} \right)$$ so, perhaps you should just break the vectors up into components, carry out the operations, and report them in cartesian coordinates, or perhaps in unit vector components? i don't know, just some ideas. 31. assuming the surface of the water is the inertial reference frame, this isn't so tough. add the two vectors, find the magnitude. you got that far -- now, think of a geometric description of what you've done. you've added two vectors and now have a resulting vector in the second quadrant. you've got a triangle -- can you figure out the angle with that? 34. sounds reasonable. i can't really imagine your picture at this ungodly hour -- i do suspect that you've done it correctly. for these you add up all the vectors ala their seperate components. 40. yah, that makes two of us 43. i'm not sure on what the prefered approach to this would be either. let's say you've got triangle ABC. now, can you perhaps come up with cartesian coordinates for the midpoints of A and B? to get the vector for the new triangle produced, you'd just have to subtract one from the other, right? so, i'm sure you can see that however you do this, it will be parallel to C. what kind of vector operations depend on the angle between two vectors? (hint: *dot product*, cross product. i haven't worked any of these out, but perhaps i can at least shed some perspective on them? i'm in calc 3 now, so i'm no master at this business. cheers