△ABC中,

是A,B,C所对的边,S是该三角形的面积,且

。
(1)求∠B的大小;
(2)若
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,

,求

的值。
(1)
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(2)

(1)由

得,

,则

,所以
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,而B是△ABC内角,则


。
(2)因为
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,则

,得
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,由余弦定理得,


,所以


。
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