Differential equations can be taught using Sage as an inventive new approach. David Joyner and Marshall Hampton's lucid textbook explains differential equations using the free and open-source mathematical software Sage. Since its release in 2005, Sage has acquired a substantial following among mathematicians, but its first user was Joyner, who is credited with helping famed mathematician William Stein turn the program into a usable and popular choice. Introduction to Differential Equations Using Sage extends Stein's work by creating a classroom tool that allows both differential equations and Sage to be taught concurrently. It's a creative and forward-thinking approach to math instruction. Topics include: • First-Order Differential Equations • Incorporation of Newtonian Mechanics • Second-Order Differential Equations • The Annihilator Method • Using Linear Algebra with Differential Equations • Nonlinear Systems • Partial Differential Equations • Romeo and Juliet