a)D=R

b)D=R\{kπ}

a)y=-2sinx

TXD:D=R

Lấy x€D--->-x€D

Tacos f(x)=-2sinx

F(-x)=-2sin(-x)=2sinx=-f(x)===>hàm lẽ

a)y=2cos(x+π/3)

-1<=cos(x+π/3)<=1

<=>-2<=2cos(x+π/3)<=2

--->min=-2,max=2

a)y=2sin2x=4sinxcosx

F(x+kπ)=4.(-1)^k.sinx.(-1)^k.cosx=4.sinx.cosx=f(x)