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在《轴对称》章的学习中,我们知道对于含30°角的区角三角形,有一个很有用的结论:在直角三角形中,如果有一个锐角等于30°,那么它所对的直角边等于斜边的一半.这个结论实际上首次给出了计算线段长的方法,因而在计算长度和叫线段的倍分关系时可以发挥作用.利用它,不仅可以计算含30°角的直角三角形的有关边长,还可以计算和等边三角形、含15°角的三角形有关的问题.但需要注意的是,这个结论有前提条件:(1)直角三角形;(2)有一个锐角等于30°.
In the study of the chapter “Axisymmetric”, we know that for a zone-angle triangle with a 30 ° angle, there is a very useful conclusion: if there is an acute angle equal to 30 ° in a right-angled triangle, then the right- This conclusion, for the first time in fact, gives the method of calculating the length of a line segment and thus plays a role in calculating the length-of-fold relationship between the line segments and using it to calculate not only the right-angled triangle with a 30 ° angle Side length, but also can be calculated with the equilateral triangle, triangle angle of 15. But note that this conclusion has the prerequisite: (1) right triangle; (2) has an acute angle equal to 30 °.