find the vector having a magnitude 3 units in the direction of the resultant vector of the vector addition of vector A and vector B.vector A=i cap+ j cap; vector B=k cap

Resultant of vector A and B is, R = A + B = i + j + k

The unit vector in the direction of R is (i + j + k)/(1² + 1² +  1²)^1/2 = (i + j + k)/√3

So, the required vector is 3 × (i + j + k)/√3 = √3 (i + j + k)