the sum of three forces f1=100n, f2=80n, f3=60n acting on a particle is zero.

Question

The angle between f1 and f2 is:

Please solve

Answer 1

you don't say what n is, but it looks like all three vectors are in the same direction. It would not be possible for the sum of all three to be zero, since they are all positive

Answer 2

|F1+F2|=|F3|
Squaring both sides
|F1+F2|²=|F3|²
=>cos(theta) =37°