Ajutati-ma va rog repede
ex4
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4)
sin 20°- sin 160°= 2sin(-70)cos(90)=0
cos 20°+cos 160°= 2cos(-70)cos(90)=0
0=0(adevărat)
Răspuns:
Explicație pas cu pas:
sin 20°-sin 160°
sin 160°=sin (180°-20°)=sin 20°
sin 20°-sin 160°=sin 20°-sin 20°=0
cos160°=cos(180°-20°)=-cos 20°
cos 20°+cos 160°=cos 20°-cos 20°=0