Triangle Law of Vector Addition #8211; If two vectors are represented both in magnitude and direction by the two sides of a triangle taken in the same order, than the resultant of these vectors in represented both in magnitude and direction by the third side of the triangle taken in reverse order as shown below : R = A + B = B + A The resultant, R can be calculated as │A + B│ = │R│ = √A<sup>2</sup> + B<sup>2</sup> +2 ABcosθ Where, θ is angle between vectors A and B. if resultant R makes an angle α with vector A, then tanα = B sinθ/A + Bcosθ.