Two vectors of magnitude 8 unit each are acting at a point making an angle120 degree with each other.determine the magnitude

Answer 1

use the law of cosines:

x^2 = 8^2 + 8^2 - 2*8*8*cos(60°)

Answer 2

or just take components up the middle
2 * 8 cos (120/2) = 16 cos 60 = 8