#|hata+hatb| =√3#
#=>sqrt(abshata^2+abshatb^2+2abshataabshatbcostheta)=sqrt3#
#=>sqrt(1^2+1^2+2xx1xx1costheta)=sqrt3#
[ #abshata=1 and abs hatb=1# as they are unit vector]
#=>1^2+1^2+2xx1xx1costheta=3#
#=>costheta=(3-2)/2=1/2=cos60^@#
#=>theta=60^@#
Now
#|hata -hat b|#
#=sqrt(abshata^2+abshatb^2+2abshataabshatbcos(pi-theta))#
#=>sqrt(1^2+1^2-2xx1xx1costheta)#
#=>sqrt(1^2+1^2-2xx1xx1cos60^@#
#=>sqrt(1^2+1^2-2xx1xx1xx1/2)=1#