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

> 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);

> a:=5;

> h:=7;

> plot({f(x), secline(x), tanline(x)}, x= a-4..a+6, color=[blue,violet,magenta]);