z(a,b):=a+b*%i;

f(a,b):=cos(z(a,b));

f(x,y);

realpart(f(x,y));

imagpart(f(x,y));

realpart(f(0,1));

imagpart(f(0,1));

Cosh(e,x):=(e^x+e^(-x))/2;

Sinh(e,x):=(e^x-e^(-x))/2;

cos(x)*Cosh(2.71828,y);

-sin(x)*Sinh(2.71828,x);