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    Where there is a will(意志), there is a way. The secret of s____  is not much money but a strong will. In other words, a man can't w____   without a strong will. It is quite clear that there is nothing d____ in the world. If a person makes up his mind to do it, he will certainly r____ his goal. A student should r____  the following duties: we s____ care about our parents; we have to study as h____  as possible, we must be honest and keep our words as well. E____  of us should receive good education. Our parents send us to school to let us get k____ and wish us to be a hard-working and successful person in the future. So when we fail, don't lose heart. Keep on working u____ we succeed. Make sure nothing could prevent you from trying.

一数学兴趣小组为了测量河对岸树AB的高，在河岸边选择一点C，从C处测得树梢A的仰角为45°，沿BC方向后退10米到点D，再次测得A的仰角为30°，求树高．（结果精确到0.1米，参考数据：$\sqrt{2}$≈1.414，$\sqrt{3}$≈1.732）