Why the answer is wrong ( SIMPLE TRIGONOMETRIC)

My code is:

function onex(y)

cos(y)*cos(y)-sin(y)*sin(y)

end

When I insert y=pi/4 The result is:

>> onex(pi/4)

ans =

     2.2204e-16

Does anybody has any suggestions? Thank you in advance!

Answer 1

[Joseph Cheng]

to try to get zero as you want, you may have to do it in degrees.

x= pi/4*180/pi;
cosd(x)*cosd(x)-sind(x)*sind(x)

will get you your 0. This is because pi is not exactly pi. http://www.mathworks.com/help/matlab/ref/pi.html

[Ievgenii]

Thanks!