Question

determinati m, astfel incat vectorii u=mi+j si v=i+mj sa formeze un unghi de 120 grade

Answer 1

cos 120°= -1/2=u*v/|u|*|v|=(m*1+1*m)/√((m²+1)*√(m²+1))=2m/(m²+1)

m²+1=-4m

m²+4m+1=0

m1,2=(-4+/-√(16-4))/2=(-4+/-2√3)/2= -2+/-√3