Question

Giúp mik vs ạ

Answer 1

1: -1<=sin(x-pi/2)<=1

=>-2<=2sin(x-pi/2)<=2

=>1<=y<=5

y=1 khi sin(x-pi/2)=-1

=>x-pi/2=-pi/2+k2pi

=>x=k2pi

y=5 khi sin(x-pi/2)=1

=>x-pi/2=pi/2+k2pi

=>x=pi+k2pi

2: -1<=cos2x<=1

=>1/2>=-1/2cos2x>=-1/2

=>7/2>=y>=5/2

y=7/2 khi -1/2cos2x+3=7/2

=>-1/2cos2x=1/2

=>cos2x=-1

=>2x=-pi+k2pi

=>x=-pi/2+kpi

y=5/2 khi cos2x=1

=>2x=k2pi

=>x=kpi

3: -1<=sin2x<=1

=>-3<=3sin2x<=3

=>-8<=y<=-2

y=-8 khi sin2x=-1

=>2x=-pi/2+k2pi

=>x=-pi/4+kpi

y=-2 khi sin2x=1

=>2x=pi/2+k2pi

=>x=pi/4+kpi

4: -1<=cos(x+pi/4)<=1

=>2>=-2cos(x+pi/4)>=-2

=>9>=y>=5

y=9 khi -2cos(x+pi/4)+7=9

=>-2cos(x+pi/4)=2

=>cos(x+pi/4)=-1

=>x+pi/4=pi+k2pi

=>x=3/4pi+k2pi

y=5 khi cos(x+pi/4)=1

=>x+pi/4=k2pi

=>x=k2pi-pi/4