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cos la 2a 120 grade + sin la 2a 60 grade

Răspuns :

C04f
cos120°=cos(90°+30°)=-cos30°=-[tex] \frac{ \sqrt{3} }{2} [/tex],   sin60°=[tex] \frac{ \sqrt{3} }{2}[/tex], deci suma este = [tex] (\frac{- \sqrt{3} }{2})^2+( \frac{ \sqrt{3} }{2})^2= \frac{3}{4}+ \frac{3}{4}= \frac{3}{2} [/tex]

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