# SECTION 7.6?Heavisideu := t -> Heaviside(t);plot(u,-2..2,scaling=constrained);plot(u(t-1),t=-2..2,scaling=constrained);# Example 1f := 3*(1-u(t-2)) + 1*(u(t-2)-u(t-5)) + t*(u(t-5)-u(t-8)) + t^2/10*(u(t-8));plot(f,t=0..12,scaling=constrained);?plot #Look up how to handle discontinuitiesplot(f,t=0..12,scaling=constrained,discont=true);# Example 2with(inttrans);g := t -> t^2;a := 1;g(t+a);laplace(g(t+a),t,s);exp(-a*s)*laplace(g(t+a),t,s);# Example 3g := t -> cos(t);a := Pi;g(t+a);laplace(g(t+a),t,s);exp(-a*s)*laplace(g(t+a),t,s);# Example 4F := 1/s^2;a := 2;invlaplace(F,s,t);f := t -> t;u(t-a)*f(t-a);plot(%,t=0..5,scaling=constrained);# Example 5I^2;Redefine I:interface(imaginaryunit=j);# Check:j^2;I^2;de := diff(I(t),t,t) + 4*diff(I(t),t) = g; G := 1/s - 2/s*exp(-s) + exp(-2*s)/s;alias(J = laplace(I(t),t,s));eq := laplace(lhs(de),t,s) = G;subs({I(0)=0,D(I)(0)=0},%);solve(%,J);Jsol := %;F := 1/(s*(s^2+4));convert(F,parfrac,s);invlaplace(F,s,t);f := t -> 1/4 - 1/4*cos(2*t);Isol := f(t) - 2*f(t-1)*u(t-1) + f(t-2)*u(t-2);plot(Isol,t=0..5,-1..1);# Alternate solution using dsolve:I := 'I';de;g := 1*(u(t)-u(t-1)) -1*(u(t-1)-u(t-2)) + 0*u(t-2);de;dsolve({de,I(0)=0,D(I)(0)=0});Isol2 := rhs(%);plot(Isol2,t=0..5,-1..1);# Remark: dsolve has clearly made an error in finding this solution.# Example 6 Sum(t^(2*n+1)*(-1)^n/(2*n+1)!,n=0..3);value(%);f7 := %/t;f7 := simplify(%);laplace(f7,t,s);taylor(arctan(x),x,8);subs(x=1/s,%);