## Saturday, September 11, 2010

### teaching: conversion factors

my teaching pace is off.

since the start of my postdoc position, i've relied on the following conversion [1]:

1 calculμs lecture = 5 handwritten pages,
1 analysιs lecture = 4 handwritten pages.

lately i've been going through less material in my caΙc 3 lectures.

yesterday morning i made it through 4, not 5 pages.

my afternoon class has a different personality: there are a few students who consistently ask questions that are more involved than, say, why there is an extra negative sign present in the 2nd component of that one vector in $\mathbf{R}^3$.. [2] but more like what does
$$\int_a^b \vec{\bf r}(t) dt$$
mean? how do we interpret it (geometrically or mechanically)?

that said, yesterday afternoon, i made through only 3 pages.
the pace isn't the important thing, of course. usually topics even out over the course of the term; at worst, i could always skip some topics for reasons of time ..

.. i'm concerned about which conversion factor is at work, here:
the calcμlus rate or the analysιs rate?

it's neither an analysιs class that i'm teaching,
nor an honors calcuΙus class.

more than 1/2 of my students are engineers and non keen on theory. maybe i've given too many explanations, made too many unorthodox choices.

to liven things up -- it was a review topic from last term anyway -- my lecture on dot products began with the geometric formula, rather than the component-wise one:
$$\vec{\bf a} \cdot \vec{\bf b} = |\vec{\bf a}| |\vec{\bf b}| \cos \theta$$
i then discussed prοjections next, and when it came time for distribution formulas like
$$\vec{\bf a} \cdot (\vec{\bf b} + \vec{\bf c}) = \vec{\bf a} \cdot \vec{\bf b} + \vec{\bf a} \cdot \vec{\bf c}$$
i drew a diagram of the projections and explained why the formula was true. (this had always struck me as a more pleasant meaning, rather than something purely formulaic from components.)

the requisite computational examples came afterwards, of course, but in retrospect i wonder if i traumatised them. (i think a few students dropped my class the next day.)

since my grad school days, i've taught calcuΙus courses with this cautionary rule in mind: if i find it really interesting, then it's probably inappropriate for class.

i can't help myself, sometimes;
i get terribly bored otherwise ..

but if this is really cutting into lecture time, then maybe i should exercise more caution. \-:

[1] if you want the specifications, i use college-ruled lined paper and non-mechanical pencils: my multivariate diagrams work out better that way.

[2] some students are used to the alternating signs of 3x3 determιnants and crοss products; others are not. \-: