> restart:

> a := 1;

> f := x->cos(x);

> h := 2.2;
q:= (f(a+h) - f(a))/h;
secline:= x -> f(a) + q*(x - a);
m:= D(f)(a);
tanline:= x -> f(a) + m*(x - a);

> plot([tanline(x), f(x), secline(x)], x=-5..5, color=[blue,green,magenta]);