Only in a flat universe does space obey all the standard geometry-class rules-the angles of a triangle add up to exactly 180 degrees and parallel lines never meet.

只有在平坦的宇宙中，空间才符合标准的几何规律——三角形的内角和精确地等于180度，平行线永远不相交。

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To order, use the appropriate order code from the chart for standard or 180 degree mounting, or 90 or 270 degree mounting.

订购时，请从下列表格中选择适当的型号代码来标示安装位置是标准或180度，或者90度或270度安装位置。

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Bevel gears can be mounted at standard, 90, 180 or 270 degree mounting.

锥齿轮可以采用标准位置，90度、180度或270度位置安装。

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The 500 stocks that make money consistently each of the last four quarters are weighted based on their daily standard deviation over the last 180 trading days, compared to their average.

FORBES: Making Stock Volatility Work For The Long-Term Investor