If /U/=9, /V/=11, and theta = 43 deg (angle between), find the magnitude of U+V and give the direction that the that the resultant makes with U.

Answer 1

make a sketch by completing the usual parallelogram , if U+V = R
R^2 = 11^2 + 9^2 - 2(9)(11)cos 137°
= 346.808
R = 18.62

now use the Sine Law to findØ, the angle between V and R.
sinØ/9 = sin137°/18.62
sinØ = .329595
Ø = 19.24° with vector V, then
23.76° with vector U