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In triunghiul ABC se dau AB=4,BC=5,AC=6.Calculati cos B/2

Răspuns :

AB=c=4
BC=a=5
AC=b=6
cosB=a^2+c^2-b^2/2ac=25+16-36/2*4*5=5/40=1/8
cos B/2=rad[(1+cosB)/2]=rad ([1+1/8)/2]=rad9/16=3/4