# SECTION 4.6# Example 1# de := diff(y(t),t,t) + y(t) = tan(t);y1 := cos(t); y2 := sin(t);eq1 := y1*v1p + y2*v2p = 0;eq2 := diff(y1,t)*v1p + diff(y2,t)*v2p = tan(t);v1p := 'v1p'; v2p := 'v2p';sol := solve({eq1,eq2},{v1p,v2p}); v1p := rhs(sol[1]);v2p := rhs(sol[2]);Int(v1p,t);value(%);v1 := % + C1;v2 := int(v2p,t) + C2;y := v1*y1 + v2*y2;expand(%);# Example 2y := 'y';de := diff(y(t),t,t) + y(t) = tan(t) + 3*t -1;dsolve(de);