Question

1 in reperul cartezian xOy se considera dreapta d de ecuatie x-2 y + 1 = 0 . Determinati numarulreal a, stiind ca punctul A(a,2) apartine dreptei d .

2 . in triunghiul ABC dreptunghic in A , AB=3 si AC= 4 . Determinati sin B . 

Answer 1

1.  x-2 y + 1 = 0 
y=(x+1)/2
A(a,2)  => f(a)=2 => (a+1)/2=2 => a+1=4 =>a=3
2. sin B=c.o./i
c.o.=cateta opusa
i=ipotenuza
i=bc=V(AB2+AC2)=V(9+16)=V25=5
V=radical
AB2=AB la patrat
=> sin B=4/5