Question

Claculate the angle b/w.a 2 dyne and a 3.dyne forces so that their sum is 4 dyne

Answer 1

as you know, force is a vector quantity .and sum of two vectors a and b is √{ a² + b² + 2ab.cos∅} where ∅ is the angle between them.
now, a = 2 Dyne b = 3 Dyne R = 4 Dyne so, 4 = √{ 2² + 3² + 2.2.3 cos∅}16 = 4 + 9 + 12cos∅3 = 12cos∅ cos∅ = 1/4 ∅ = cos-¹( 1/4)