Why does Math.cos(90 * Math.PI/180) yield 6.123031769111... and not zero? [duplicate]
The output of
Math.cos(90 * Math.PI/180)is
6.123031769111886e-17Notice the e-17 at the end, which means that this number is 6.123 x 10-17. This is a number so vanishingly close to 0 that it's effectively 0. The reason that it's not identically 0 is due to rounding errors in the IEEE-754 double format which prevents you from getting an exact representation of π / 2 and causes minute rounding errors in the calculation of the cosine.
By the way - I was pretty surprised as well when the result came back starting with a 6! It's only after I looked at the very end that things started to make sense.
Hope this helps!
6.123233995736766e-17is scientific notation for a very small number, close to zero. It is not exactly zero because of rounding errors and so forth.
6.123233995736766e-17 is very very close to zero. Just round the number.