已知△ABC中,∠A=2（∠B+∠C）,则∠A的度数为（ ）.A.100° B.120° C.140° D.160°

已知△ABC中,∠A=2（∠B+∠C）,则∠A的度数为（ ）.A.100° B.120° C.140° D.160°
已知△ABC中,∠A=2（∠B+∠C）,则∠A的度数为（ ）.A.100° B.120° C.140° D.160°

已知△ABC中,∠A=2（∠B+∠C）,则∠A的度数为（ ）.A.100° B.120° C.140° D.160°
已知△ABC中,∠A=2（∠B+∠C）,则∠A的度数为（B.120° ）.A.100° B.120° C.140° D.160°
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a = 2*(b+c)
a+b+c=180
1.5a=180
a = 120

∠B+∠C=180-∠A ∠A=2（∠B+∠C）=2（180-∠A）=360-2∠A 3∠A=360
∠A=120 选B