Math.cos() gives wrong result

问题

According to Wolfram Mathematica: cos(50) = 0.6427876096865394;

But this code in Java:

    System.out.println(Math.cos(50));

gives 0.9649660284921133.

What is wrong with java.lang.Math?

回答1:

Math.cos() expects the parameter to be in radians. This will return the result you need:

Math.cos(Math.toRadians(50));

回答2:

Math.cos() uses radians, so to get your expected result you need to do

System.out.println(Math.cos(Math.toRadians(50)));

回答3:

Most Java trigonometric functions expects parameters to be in radians. You can use Math.toRadians() to convert:

System.out.println(Math.cos(Math.toRadians(50)));

回答4:

Degrees <> radians...........

回答5:

For me...

System.out.println(Math.cos(50));
System.out.println(Math.cos(new Double(50)));
System.out.println(Math.cos(Math.toRadians(50)));
System.out.println(Math.cos(Math.toRadians(new Double(50))));

returns

0.9649660284921133
0.9649660284921133
0.6427876096865394
0.6427876096865394

http://www.wolframalpha.com/input/?i=cos%2850deg%29

cos(50deg) give same result as cos(50)... so Wolfram is degree by default.

来源：https://stackoverflow.com/questions/12975924/math-cos-gives-wrong-result