Math.Cos & Math.Sin in C#

Let me answer your question with another one: How far do you think 6.12303176911189E-17 is from 0? What you call deviance is actually due to the way floating point numbers are internally stored. I would recommend you reading the following article. In .NET they are stored using the IEEE 754 standard.

See answers above. Remember that 6.12303176911189E-17 is 0.00000000000000006 (I may have even missed a zero there!) so it is a very, very small deviation.

you should use rounding

var radians = Math.PI * degres / 180.0;
var cos = Math.Round(Math.Cos(radians), 2);
var sin = Math.Round(Math.Sin(radians), 2);

the result would be: sin: 1 cos: 0