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Ex 5 dau coroana!!!!!!

Ex 5 Dau Coroana class=

Răspuns :

Răspuns:

Aplicam formula:

cos(180-x)=-cosx

doar daca x este intre 90 si 180

cos160=cos(180-160)=-cos20

cos170=cos(180-170)=-cos10

cos10+cos20+cos160+cos170=cos10+cos20+-cos20+-cos10=0+0=0