Question

Hei, mă puteti ajuta la b va rog?

Answer 1

aplic formula
sin a+sinb=2sin (a+b)/2*cos(a-b)/2
deci avem
2sin (2x+225+2x-45)/2*cos(2x+225-2x+45)/2=
2sin (4x+180)/2*cos 270/2=
2 sin (2x+90)*cos 135=

dar cos 135=-rad2/2

2*(-rad2/2)*sin (2x+90)=
-rad 2*sin (2x+90)

rezolvam sin(2x+90)=sin 2x*cos90+cos2x*sin 90=cos2x
cos90=0
sin90=1

deci rezultat final -rad2 *cos2x