The angle between the vectors (i^+j^) and (j^+k^) is:
900
600
300
450
Let, A→=i^+j^ and B→=j^+k^
A→.B→=(i^+j^).(j^+k^)=1
Also,|A→|=(1)2+(1)2=2
|B→|=(1)2+(1)2=2
Now cosθ=A→.B→|A→|.|B→|=12×2=12
θ=cos−1(12)=600