Question

Угол между прямыми AB и AC. 
A(3. -2)
B(2. -4)
C(4. 3)

Answer 1

$AB (2-3;-4+2) = (-1;-2)\ AC (4-3;3+2) = (1;5)\ \ cosa=frac{1*-1-2*5}{sqrt{1^2+2^2}*sqrt{1^2+5^2}}=frac{ -11}{sqrt{130}}$