Is line L1 perpendicular to L2 ?
1. L1 passes through (1,2) and L2 passes through (2,1)
2. L1 is parallel to x=y and L2 is parallel to x-y+4=0
1. L1 passes through (1,2) and L2 passes through (2,1)
2. L1 is parallel to x=y and L2 is parallel to x-y+4=0
















