Question

Ma asculta luni ...si vreau sa repet exercitiile ,dar nu stiu cum se rezolva...
Cu formulele urmatoare :
Sin(a+b)=sina×cosa+sina×cosa=>sin2a=2sina×cosa
Si
Cos(a+b)=cosa×cosb+sina×sinb=>cos2a=cosa+sina(la a doua)
Calculati :
Sin 120,si cos 120
Va rog..

Answer 1

sin 120=sin (90+30)=sin90××cos30+cos90×sin30=√3/2

cos 120= cos(90+30)=cos90×cos30-sin90×sin30=-1/2

Answer 2

sin(120)=sin(30+90)=sin30×cos90-cos30×sin90= 1/2×0-√3/2×1=√3/2

cos(120)=cos(30+90)=cos30×cos90-sin30×sin90= √3/2×0-1/2×1=1/2

si ca sa intelegi
sin(a+b)= sin a × cos b + cos a × sin b
sin(a-b) = sin a × cos b - cos a × sin b
cos(a+b) = cos a × cos b - sin a × sin b
cos(a-b) = cos a × cos b + sin a × sin b

sper ca te-am ajutat