名词
中文翻译：延长器
同义词：
['extender', 'extender', 'elongator']
例句：
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1.The protractor is used to measure the length of a line when it's not perpendicular to the ground.
延长器用于测量一条线在不垂直于地面时的长度。
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2.The protractor was used in ancient times to measure the angles between two lines.
古代使用延长器来测量两条线之间的夹角。
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3. In engineering, the protractor is used to measure the angles of a plane with respect to a reference plane.
工程中，延长器用于测量一个平面相对于参考平面的角度。