Derivatives of Vector Functions

Desmos -- Derivatives of Vector Valued FunctionsOne way to think of a curve in the plane (or in space) is as a collection of terminal points of vectors whose initial points are all at the origin.  The vectors are given by a vector-valued function.

For example, the parabola shown at right can be thought of as the graph of the vector-valued function

r(t) = < t , (t-1)^{2}+1>

I’ve created a Desmos demonstration that shows how graphs of vector-valued functions are related to their vectors (shown in blue), and how the derivative of a vector-valued function is related to both difference vectors and tangent vectors.  You can access the demonstration here.

You can find more of my Desmos demonstrations here.

Exponentials and Ebola

My latest piece for the New York Times Learning Network is a lesson on the underlying mathematics of the spread of contagious diseases, like Ebola.ebola map

In this lesson, students use a basic exponential model to explore the fundamental mathematical ideas of transmission and replication.

Mathematically, the spread of disease can be modeled in a manner similar to the spread of a rumor. Although a number of simplifying assumptions must be made, the simple exponential model captures the basic impact of transmission rates on the dispersion of a disease among a population. Students can explore the consequences of transmission rate using multiplication, algebra, graphing utilities and elementary statistics.

After exploring the essential behavior of various simple exponential models, students then compare real-world data to their theoretical models.  Those that are capable can perform regressions on the data to approximate actual transmission rates.  The students’ work and the real-world data establish a context for discussing the strengths and weaknesses of this simple model of disease transmission.

This lesson is part of a series of Ebloa lessons at the NYT Learning Network and is freely available here.

MfA Workshop — Surfaces in Space

surfaces in space workshopI’m looking forward to a a workshop I’ll be running tonight at the Math for America offices on three-dimensional coordinate geometry.

This workshop will cover the basic algebraic and geometric techniques for analyzing functions and relations in x, y, and z, as well as some simple methods for building interesting surfaces in space.

Sketching in space is a favorite topic of mine, and I’m really excited to share it with a group of MfA teachers.  Three-dimensional coordinate geometry is an accessible, fun, and rich area that few math teachers have experience with.  But given the advances in graphing technology and the applications to 3D printing, it’s something that more people can, and should, learn about!

 

Common Core and “Who Needs Algebra?”

Every so often, some variant of the question “Is Algebra Necessary?” comes to the fore in our national conversation on math education.

As I’ve written before, conversations like this don’t bother me.  I love math and I love teaching math, but I think the underlying questions here, “How much math, and what math, should everyone be required to know?”, are legitimate and worthy of serious consideration.  The mere fact that it keeps coming up suggests we don’t have great answers to these questions, or even great explanations as to why things are the way they are.

So I’m always interested in pieces like NPR’s “Who Needs Algebra?”, which describes how colleges around the country are trying to address the problems created by algebra requirements.  According to NPR, nearly 50% of community college students fail to graduate because they can not pass a required algebra course.  For this reason, algebra is often called a gatekeeper course, as it prevents access to the credential of a college degree.

As the piece notes, colleges are doing some interesting and innovative things to try to get students around the algebra requirement.  One particular approach, developed by the Community College Pathways initiative, offers statistics and quantitative reasoning courses that “largely skip over abstract algebraic formulas and go directly to math concepts that students will use and find engaging”.  The piece speaks positively about this new approach, which I think has merit and deserves attention.

But I can’t help but wonder how this fits in with the Common Core standards initiative.  The Common Core state math standards mandate a substantial amount of algebra in junior high and high school.  In many cases, this is the same algebra that colleges are attempting to circumvent in order to increase graduation rates.  How can mandatory algebra in high school be reconciled with optional algebra in college?

I think about Common Core, too, when I read about the great work Cornell professor Steven Strogatz is doing in “teaching math to people who think they hate it“.  Strogatz, both a renowned mathematician and teacher, is implementing a curriculum based on Westfield State University’s Discovering the Art of Mathematics, and is finding great success reaching math-averse liberal arts students with its activity- and inquiry-based approach.  But can this type of course, that excites and engages students in authentic mathematics while eschewing the typical trappings of a traditional algebra curriculum, be reconciled with the mandatory algebra standards set forth in the Common Core?  [Strogatz shared some of his informed opinions about math education in his Math Horizons interview last year.]

I don’t believe these various positions are completely incompatible, but I do see a fundamental conflict here.  After all, if a reasonable argument can be made that “Not everyone needs algebra”, then mandating algebra for everyone seems likely to create as many problems as it attempts to solve.

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