JavaScript浮点精度问题 [英] JavaScript floating point precision issue

问题描述

我遇到浮点精度问题，有人知道为什么会这样吗?为什么余弦函数会受到影响，而正弦函数却没有受到影响.

I am encountering a floating point precision issue, does anybody know why this happens? Why is it that the cosine function is affected, but not he sine function.

Math.sin(90 * Math.PI / 180);
// returned: 1, expected: 1

1 - Math.sin(90 * Math.PI / 180);
// returned: 0, expected: 0


Math.cos(90 * Math.PI / 180);
// returned: 6.123233995736766e-17, expected: 0

1 - Math.cos(90 * Math.PI / 180);
// returned: 0.9999999999999999, expected: 1

推荐答案

对此的典型答案是再进行一些尝试，您将发现使用正弦函数获得意外"结果的示例.

With a little more trying you will find examples for "unexpected" results with the sine function.

例如Math.sin(180 * Math.PI / 180);

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