{ x3 = piecewise(1/100*sin(1571/1000000*(-500 + t)), and(t > 500, t < 250254614894971/100000000000), 0),
  2*k2*x1 + 2*k2*x2 + 4*k2*x4 + 4*k1*x5 + 2*k1*x6 + 2*k1*x7 = k1*k19 + k2*k18 }