2. f(x) <\ 2
x^2- x -2 <\0
delta= 1+8= 9
x1= (1+3)/2= 2
x2= (1-3)/2 = -1
deci x apartine [-1, 2]
6. sin2x = 2sinx × cosx
Putem folosi formula (a+b)^2 = a^2 +2ab+ b^2 pt a le aplica pe amandoua
sin^2 x + cos^2x= 1^2= 1
Rezolvare: (sinx + cosx)^2= sin^2 x + 2sinxcosx + cos^2x
1= 1+2sinxcosx
2sinxcosx = 0
sin2x=0
