This double-barrelled WitCH comes from *Maths Quest Mathematical Methods 11* (top). and *Cambridge Mathematical Methods 1 & 2* (bottom). It is the final in our series of Quest-bashing, at least for now.

# Tag: transformations

## WitCH 43: Period Piece

This one comes courtesy of a smart VCE student, the issue having been flagged to them by a fellow student. It is a multiple choice question from the 2009 Mathematical Methods, Exam 2; the Examination Report indicates, without comment, that the correct answer is D.

### UPDATE (08/12/23)

The exam report was amended on 18/09/2020, after this post appeared. The report now includes a note, with no indication that the note was added a decade later:

*B was also accepted as it leads to an equivalent expression.*

If true, then the original exam report was consciously deceptive.

## WitCH 28: Tone Deaf

We haven’t yet had a chance to go through the 2019 VCE exams, but this question was flagged to me independently by two colleagues: let’s call them Dr. Death and Simon the Likeable. It’s from Mathematical Methods Exam 2 (CAS). (No link yet.)

**UPDATE (05/07/20)**

And then there’s Part (e). “This question was not answered well” the examiners solemnly intone. Gee, really? Do you think your question being completely stuffed might have had something to do with it? Do you think maybe having a transformation of *x* when there’s not an *x* in sight may have been just a tad confusing? Do you think that the transformation then resulting in a function of *t* was maybe not the smartest move? Do you think writing an integral backwards was perhaps just a little too cute? Do you think possibly referring to the area of, rather than to the value of, an integral was slightly clunky? And, most importantly, do you think perhaps asking a question for which there is an infinite and impenetrable jungle of answers may have been an exercise in canyon-sized incompetence?

But, sure, those troublesome students didn’t answer your question well.

Part (e) was intended to have students find a transformation of the function *f* that effectively switches the behaviour on the intervals [0,4] and [4,6] to the intervals [2,6] and [0,2]. Ignoring the fact that the intended question was asked in an absurdly opaque manner, and ignoring the fact that no motivation for the intended question was either provided or is imaginable, the question asked was entirely different, and was ridiculous.

Writing the transformation out,

we then have

So, the function~~ ~~ *y* = *f*(*t*)*y* = *f*(*x*) can be written

Solving for *Y*, that means our transformed function *Y* = *g*(*X*) can be written

Well, this is our function *g* unless *a* = 0, in which case *g* doesn’t exist. Whatever. Back to the swill.

Using the result from Part (d), we have Part (e) asking for *a*, *b*, *c* and *d* such that

What then are the solutions to this equation? The examination report lists a couple of families and then blithely remarks “There are other solutions”. Really? Then why didn’t you list them, you clowns?

We’ll tell you why. Because the complete solution to this monster is a God Almighty multi-infinite mess. As a starting idea, pick any three of the variables, say *a* and *b* and *c*, to be whatever you want, and then try to adjust the fourth variable, *d*, to solve the equation. We’ll offer a prize for anyone who can give a complete solution.