COS((X-1/2)*(Y-1/2)*60)/5
-COS(6.28*X)*SIN(6.28*Y)/4
(SQR((X-1/2))+SQR((Y-1/2)))
SIN(64*(SQR(X-1/2)+SQR(Y-1/2)))/(SQR(X-1/2)+SQR(Y-1/2))/128