If angle btwn A and B is @. vector component of A prpndicular to B is Asin@.

frm cross product rule

ABsin@ = |AXB|

 

Asin@ = |AXB| / |B|     [this is for the magnitude of the component only,

                                  direction is either (j-i) or (i-j)]

                          AXB = +k or -k

                            |AXB|= 1

                          |B| = 2

so Asin@= 1/2(j-i)             option (A)