(2)由6ec8aac122bd4f6e解得6ec8aac122bd4f6e,由余弦定理得:6ec8aac122bd4f6e,化简得6ec8aac122bd4f6e解方程得6ec8aac122bd4f6e=4或6ec8aac122bd4f6e=5,检验:当6ec8aac122bd4f6e=4时,则6ec8aac122bd4f6e,又6ec8aac122bd4f6e但与条件不符,舍去;当6ec8aac122bd4f6e=5,满足题意.

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