Gaokao Math Practice Question
7. (5 分) 在 $\triangle A B C$ 中, $\cos \frac{C}{2}=\frac{\sqrt{5}}{5}, B C=1, A C=5$, 则 $A B=（ ）$
- A.$4 \sqrt{2}$
- B.$\sqrt{30}$
- C.$\sqrt{29}$
- D.$2 \sqrt{5}$
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