physics-- vector solutions
I see that your inquiry was some time ago, so maybe you got answers that are useful to you.
Let's start with the concept of vector first. A vector is a force or motion in a specific direction. If you need to walk ten blocks due north to get to school, walking ten blocks east is not going to get you where you want to go.
Vectors can be combined for a net result. If for example, you walk four blocks due east, then walk three blocks due south, you have created the two legs of a right triangle whose hypoteneuse would be five blocks long. So-- five blocks would be the net distance between your starting point and your ending point, even though you walked seven blocks to get there.
Vectors can be analyzed-- broken down into x and y values on a set of cartesian co-ordinates. Your first problem-- A is straight along the y-axis. From this you know that its only value is its y value-- there is no x value.
Vector C points along the x axis-- it therefore has no y value.
Bector B points at an angle 60 degrees above the x axis, and extends for 200 units. You can measure how far it extends along both the x and y axes, or you can use trigonometry to calculate the values for x and y.
The sine of this angle times the 200 units will produce the value for y;
The cosine of this angle times the same 200 units will produce the value for x.
Hope this helps.