(a-c)²=b²-ac则∠B=

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(a-c)²=b²-ac则∠B=(a-c)²=b²-ac则∠B=(a-c)²=b²-ac则∠B=(a-c)²=b²-ac

(a-c)²=b²-ac则∠B=
(a-c)²=b²-ac则∠B=

(a-c)²=b²-ac则∠B=
(a-c)²=b²-ac
a^2+c^2-2ac=b^2-ac
a^2+c^2-b^2=ac
cos∠B=(a^2+c^2-b^2)/(2ac)=1/2
∠B=60°