toan kho, lam ko ra

M

minvip501

E xem lai de bai kai nha
vi tinh ra no nhu the nay nay
co AM/AC=AM/AB=cos(BAC)
e ap dung dinh ly ham cos trong tam jac
co cos(BAC)=(AB^2+AC^2-BC^2)/(2*AB*AC)=1-(1/2)*(BC/AB)^2
=>AM/AC=1-(1/2)*(BC/AB)^2
thuc ra de sai la do ng ra de ap dung sai dinh ly ham cos
than
 
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