arătați ca :1+sin x=2cos^2 (pi/4-x/2)

Răspuns :

aplicam formula cos 2y=2cos^2(y)-1
ecuatia noastra devine
sinx=2cos^2 (pi/4-x/2)-1 unde consideram y=pi/4-x/2
sinx=cos2*(
pi/4-x/2)
sinx= cos(pi/2-x)   se aplica cos(pi/2-a)=sina
sinx= sinx