sin(90°-30°)=cos(90°-60°)
sin90°cos30°-sin30°cos90°=cos90°cos60°+sin90°sin60°
<=>1*√3/2 - 1/2 *0=0*1/2 +1*√3/2
<=>[tex]\frac{\sqrt{3} }{2} =\frac{\sqrt{3} }{2}[/tex](ADEVARAT)
Sau efectuam diferenta din paranteza : sin(60°)=cos(30°) <=>√3/2=√3/2 (A)
Sau cu formulele: [tex]sin(\frac{\pi }{2} -x)=cosx ~si~ cos(\frac{\pi }{2}-x) =sinx[/tex]
