Does sin() have an error?

From the command line: >> 6*pi

ans =

   18.8496

>> sin(ans)

ans =

-7.3479e-16

Really? Is that a rounding error? Is there a way to get the correct value?

Answer 1

[Matt Fig]

That is the correct value for floating point arithmetic.

sin(pi)  % Same as your example.

If you want to get the exact value, use the symbolic toolbox.

double(vpa('sin(pi)'))

[Patrick Kelley]

Yeah, I said rounding error when I meant precision error. Good old floating point binary format... I haven't used the symbolic toolbox much but I'll give it another look. Thanks for the quick answer.