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To see what the values are, write a loop that increments the degrees by 30 and goes from 0 to 360
and prints out three columns of degrees, sin and cos.

When I called toRadians() with degrees and used its value for the cos() and sin() methods, the results were as expected:

System.out.println("cos(90)="+Math.cos(Math.toRadians(90)));

This suggests that you have not read the API doc. Is the 270 degrees or radians?

Have you read the API doc for those methods to see how they work?