It has the function, in other words, of negating its own meaning in another semiotic system, in this case the semiotic system of the stoplight.

也就是说，他有这样那样的功能，在不同语义系统中表示的甚至完全相反，就像红灯表示的这些不同含义一样。

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His idea was, the formula written for the opposite one will have the opposite angle; That turns out to be the correct answer.

他的方法是,反过来的方程,以相反的角来表示,那就能推出正确的答案了

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