Improved pedagogy for linear differential equations by reconsidering how we measure the size of solutions

ABSTRACT

For over 50 years, the learning of teaching of a priori bounds on solutions to linear differential equations has involved a Euclidean approach to measuring the size of a solution. While the Euclidean approach to a priori bounds on solutions is somewhat manageable in the learning and teaching of the proofs involving second-order, linear problems with constant co-efficients, we believe it is not pedagogically optimal. Moreover, the Euclidean method becomes pedagogically unwieldy in the proofs involving higher-order cases. The purpose of this work is to propose a simpler pedagogical approach to establish a priori bounds on solutions by considering a different way of measuring the size of a solution to linear problems, which we refer to as the Uber size. The Uber form enables a simplification of pedagogy from the literature and the ideas are accessible to learners who have an understanding of the Fundamental Theorem of Calculus and the exponential function, both usually seen in a first course in calculus. We believe that this work will be of mathematical and pedagogical interest to those who are learning and teaching in the area of differential equations or in any of the numerous disciplines where linear differential equations are used.

KEYWORDS:

• Pedagogy
• second-order differential equations
• higher-order differential equations
• linear differential equations
• ordinary differential equations
• initial value problems
• a priori bounds
• taxicab geometry
• Manhattan distance
• Uber metric
• uniqueness of solutions

AMS CLASSIFICATION:

• 34A12
• 34-01
• 34-02 (MSC 2010)

Disclosure statement

No potential conflict of interest was reported by the authors.