Question

ajutor la 6 ca rog frumos

Answer 1

$cos120= 2cos^{2}60-1= 2*\frac{1}{2^{2}}-1=2*\frac{1}{4}}-1=\frac{1}{2}-1=-\frac{1}{2}\\cos120-cos45+sin30=-\frac{1}{2}-\frac{\sqrt{2}}{2}+\frac{1}{2}=-\frac{\sqrt{2}}{2}$