Therefore, when observing the sundial, it is important to first find out the projection position in the two different periods.
所以在观察日晷时，首先要了解两个不同时期晷针的投影位置。
Therefore, when observing the sundial, it is important to first find out the projection position in the two different periods.
所以在观察日晷时，首先要了解两个不同时期晷针的投影位置。
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