SIN work but COS return bad values (AtomPRO&BB)

Hello,

I have problem with COS function.
SIN work but COS return bad values.

enablehservo
x var sword
y var sword
i var long
debut
x = sin(i) * 80
y = cos(i) * 80
hservo [P0\x]
hservo [P1\y]
i = i + 1
pause 50
goto debut

This sample code must draw circle with pan&tild servos.
I must use cos(i) = sin(i + 63) to make the sample to work.

enablehservo
x var sword
y var sword
i var long
debut
x = sin(i) * 80
y = sin(i + 63) * 80
hservo [P0\x]
hservo [P1\y]
i = i + 1
pause 50
goto debut

Thanks,
Pascal