When vector n^=ai^+bj^  is perpendicular to (i^+j^) , then a and b

1=a2+b2 or     a2+b2=1                     ……(i)And   (ai^+bj^).(i^+j^)=0 or        a+b=0    or  b=−a From (i) a2+(−a)2=1  or a=12  and b=−12