Salut,
sin(15grade)=sin(45grade-30grade)
sin(45grade)cos(30grade)-cos(45grade)sin(30grade)
✓2/2×✓3/2-✓2/2×1/2
✓6/4-✓2/4=(✓6-✓2)/4
cos(105grade)=cos(45grade+60grade)
cos(45grade)cos(60grade)-sin(45grade)sin(60grade)
✓2/2×1/2-✓2/2×✓3/2
✓2/4-✓6/4=(✓2-✓6)/4
sin(135grade)=✓2/2
cos(210grade)= - ✓3/2
Spor!