# Dear Dirichlet, Issue 10

Letter writing, hospital visits, and getting the family active are among the topics of discussion in this issue’s Dear Dirichlet advice column

Moonlighting agony uncle Professor Dirichlet answers your personal problems. Want the prof’s help? Send your problems to deardirichlet@chalkdustmagazine.com.

### Dear Dirichlet,

Boy, am I in a world of woes! In the coming months, I have to go into surgery six times for a whole host of illnesses. To its credit, the hospital has allowed me to arrange my own schedule. In your doctoral opinion, which procedures should I undergo first?

— Under the weather, Cambridge

Dirichlet says:

Bypass, Intestinal, Dental, Myotomy, Appendectomy, Septoplasty: the usual order of operations. If you’re in the US, insurers will insist on Pacemakers, Excision, Myotomy and then D, A, S, which is unfortunate as you don’t need the first two things doing. Remember, only genius will get this right, and American healthcare is a disaster anyway.

### Dear Dirichlet,

I’ve decided to get the family active. No more lounging around in our pyjamas after 9am, watching Super Mario Maker streams on Twitch! I’m starting by getting the children to bike around the neighbourhood after breakfast. The youngest is 3 months old, and I’m struggling to find something appropriately sized. Know any good retailers?

— Luigi, Dallas

Dirichlet says:

No need to go shopping, just bring in the Floyd–Warshall algorithm. Simply use it on all pairs of vertices $(u,v)$ and then find the pair that minimises $\operatorname{dist}(u,v)+\operatorname{dist}(v,u)$. Since this represents a path from $u$ to $v$ and then back to $u$, that will find you the smallest cycle.

I notice you’ve included a donation of \$3 in your letter and a lot of letter ‘R’s. Thanks for the continued support. Appreciate it.

### Dear Dirichlet,

I need to paint large letters on the side of my science communication-themed narrow boat — “Yes! It’s LAVA!” etc. I’m finding getting the spacing right between the characters a bit tricky though. The pairs “Ye” and “VA” are particularly difficult. Do you know any guides which can help?

— Times New Showman, Edgbaston

Dirichlet says:

I, too, have enjoyed many hours idling through the beautiful canals of Birmingham on a barge with my badgers. With regard to your lettering, you may just find it easier to use a computerised typesetting system. Attract millions of pounds of funding and media interest by taking something we’ve been doing for years and renaming it ‘machine kerning’.

### Dear Dirichlet,

I work in a timber firm and I’m pretty sure a colleague is stealing my logging equipment. Chainsaws, planes, flannel shirt… They’ve been disappearing all year but it’s been worse since April. I tried to catch the thief recently by hiding just out of range, but I missed them by a whisker. Have you heard of such a thing before? I know it sounds like a conspiracy.

— Lumber Jack, The Box

Dirichlet says:
What you have there, Jack, is a devious toolbox plot. You say you noticed it starting after the first quartile of the year? Of course you did, but fret not, by the end of the third quartile, everything will quieten down.

I’m sorry to hear your story but I will repeat what I’ve been telling my students forever: label your axes.

### Dear Dirichlet,

How many Platonic liquids are there?

— Sofia, Bulgaria

Dirichlet says:

Two.

## Heed Professor Dirichlet’s previous advice:

• ### Read Issue 19 now!

Drinks orders, integer mysteries and the new LMS president feature in our SS24 issue! Plus all your favourite puzzles & columns.
• ### Dear Dirichlet, Issue 19

Game shows, flight and social media bots are among the problems solved in this issue's Dear Dirichlet agony aunt column
• ### Prize crossnumber, Issue 19

Can you solve it?
• ### Which houseplant are you?

Find out by following our simple flowchart
• ### Poetry corner

Thankfully not by Torquil Farquhar de Smith
• ### Top ten: Mathematical norms

The undisputed chart of the best mathematical norms this season