In this paper, the existence theorem of midpoint chord of quadratic curve, as well as its proof, is given via methods of projective geometry and polarity principle.
文章利用射影几何方法及配极原理给出二次曲线中点弦存在性定理的证明。
As the top surface of all truss chords are required to follow the surface geometry of the roof, this has the effect of requiring that top chord boxes will twist along their length.
屋顶的最高表面的全部几何学能被定义为金牛座的内部表面。所有桁架弦杆的最高表面必须要遵循屋顶的表面几何学，将会产生需要的效果，顶部的弦杆会沿着他们的长度而扭曲。
As the top surface of all truss chords are required to follow the surface geometry of the roof, this has the effect of requiring that top chord boxes will twist along their length.
屋顶的最高表面的全部几何学能被定义为金牛座的内部表面。所有桁架弦杆的最高表面必须要遵循屋顶的表面几何学，将会产生需要的效果，顶部的弦杆会沿着他们的长度而扭曲。
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