If b is added to c = 3.9i + 3.7j, the result is a vector in the positive direction of the y axis, with a magnitude equal to that of c. What is the magnitude of b?
2. The attempt at a solution
I've probably just been staring at these problems for too long...
First of all, is it valid to say the magnitude of a is the sum of the magnitudes of b and c, that is a=b+c ?
Because if so, then c=sqrt(3.9^2+3.7^2)=a
and if a=b+c then b=a-c= 0 ... which is wrong ):
so what should I do?