C# - Why is Math.Atan(1) != anything near 45.

Question

There is another post here about Atan but I dont see any relevant answers:

http://stackoverflow.com/questions/311501/c-why-math-atanmath-tanx-x

Isn't Math.Atan the same as tan-1? On my calculator I do:

tan-1(1) and i get 45.

tan(45) = 1

In C#:

Math.Atan(1) = 0.78539816339744828 // nowhere near the 45.

Math.Tan(45) = 1.6197751905438615 //1 dp over the < Piover2.

Whats happening here?

Answer 1

Math.Atan returns a value in radians. Your calculator is using degrees. 0.7853... (pi/4) radians is 45 degrees. (And conversely Math.Tan(45) is telling you the tan of 45 radians.)

Answer 2

C# is treating the angles as radians; your calculator is using degrees.

Answer 3

Your calculator is in Degrees, C# is doing these calculations in Radians.

To get the correct values:

int angle = 45;  //in degrees

int result = Math.Tan(45 * Math.PI/180);

int aTanResult = Math.Atan(result) *180/Math.PI;