Thanks a lot for the quick answer. However, I don't know how you come up with that -1 and 0 ?
The only law i know is "cos^2(theta) + sin^2(theta) = 1"
Edit: sir, I am an idiot. I overlooked what I learned previously about Pi being 180 degrees. I used the Pi function in the calculator instead of using its radian value.
PI is the ratio of the circumference and the diameter of a circle. A unitless number.
There are PI Radians in 180 degrees which comes from the circumference of a circle is 2*PI*r; 360 deg in 2*PI radians hence PI radians in 180 degrees.
Calculators like to power up in radians mode and don;t like to tell you what mode it's in. Always check a known value like cosine of 180 degrees. If the cos(180) is -1, your in degree mode.
I do the following : Degree * (Pi/180) = radians
Once I have the radians, I hit the "S <-> D" key of my calculator to get the Pi radian fraction and I know that Pi is always the numerator.
I know using that key is weak but it works well