 #1
Alexandra Fabiello
 42
 1
 Homework Statement:

Two position vectors lie in a plane. The first, vector
rA,
points at an angle of 20° below the positive xaxis and has a magnitude of 55.0 m. The second, vector
rB,
points at an angle of 47.0° above the positive xaxis and has a magnitude of 75 m.
What is the magnitude and direction of vector
rC if rA + rB = rC? Give the direction as an angle measured counterclockwise from the positive xaxis.
 Relevant Equations:

a^2 = b^2 + c^2 ?
not sure what else
I am admittedly entirely confused as to where to start, sorry.
This is the diagram I'm given that fits with the rA + rB.
If rB is 47.0 degrees above the xaxis normally, it would be the same counterclockwise here, right? Then 180  47 = 133 degrees for the clockwise angle. But now I'm stuck with how to find rC. If I assume this is actually a right angle triangle, rC ends up being about 93 degrees, but I can't really be sure it's really a right angle, so how do I do that? The book is confusing in this area, and so was the teacher.
If this is better on another thread, please let me know which one.
If rB is 47.0 degrees above the xaxis normally, it would be the same counterclockwise here, right? Then 180  47 = 133 degrees for the clockwise angle. But now I'm stuck with how to find rC. If I assume this is actually a right angle triangle, rC ends up being about 93 degrees, but I can't really be sure it's really a right angle, so how do I do that? The book is confusing in this area, and so was the teacher.
If this is better on another thread, please let me know which one.