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Aratati ca: 2arcsin2/7=arccos41/49



Răspuns :

rezolvare in atasament
Vezi imaginea BUBU1374
Aplici  cosinusul in  ambii  membrii
cos(2arcsin2/7)=cos(arccos41/49
Aplici  in  membrul  stang formula cos2x=cos²x-sin²x
cos²arcsin2/7-sin²arcsin2/7=41/49
Aplici  formula cos²x=1-sin²x
1-sin²arcsin2/7-sin²2/7=41/49
1-2sin²arcsin2/7=41/49
1-2*(2/7)²=41/49
1-2*4/49=41/49
(49-8)/41=41/49