1), Solve Equation (2.2) exactly for X 1 ( t + Δ t ) = Φ ( t , X ( t ) ) ;

2), Approximate numerically the equation (2.3)

For X 2 ( t + Δ t ) with initial condition

X 2 = X 1 ( t + Δ t ) , then

X 2 ( t + Δ t ) = X 1 ( t + Δ t ) + α ( X 1 ( t + Δ t ) , t ) Δ t +

3) Take X ( t + Δ t ) = X 2 ( t + Δ t ) . Thus

X ( t + Δ t ) = Φ ( t + Δ t , X ( t ) ) + α ( Φ ( t + Δ t , X ( t ) ) , t ) Δ t +