### $-e^{i\pi}$ to Watch: 3Blue1Brown

In this series of posts, we’ll be featuring mathematical video and streaming channels from all over the internet, by speaking to the creators of the channel and asking them about what they do.

We spoke to Grant Sanderson, author of the 3Blue1Brown channel, which now has over 5 million subscribers and has been posting videos since about 2016.

### What Can Mathematicians Do? Recordings of ten talks by disabled mathematicians

In December I organised a series of online public maths talks called What Can Mathematicians Do?

The recordings of the talks are now online, free for anyone to watch. You could go to the official page I put up on Newcastle University’s website, or you could just watch them here!

### How to fold and cut a Christmas star

This week and last I hosted a series of public maths talks featuring disabled presenters. I’ll post about how that went later, but for now I just want to share this clip of me filling time spreading Christmas joy.

This is a party trick that Katie Steckles showed me: you can fold a piece of paper and then make a single cut to produce a five-pointed star. I showed how to do it by following the instructions I’d been told, and then recreated the steps just starting from the insight that when you make the cut, all the edges of the shape need to be on top of each other.

Maybe you’ll show someone else how to do it during the Christmas holiday?

This doesn’t only work for stars: there’s a theorem that you can make any polygon by folding and a single cut. Erik Demaine has made a really good page about the theorem, with some examples to print out and links to research papers. Katie can cut out any letter of the alphabet on demand, which is impressive to witness!

### Katie shows you how to make a kumihimo braid

The Queen Elizabeth Prize for Engineering and Alom Shaha have organised a Month of Making – each day, a different person shows how to make a nice handmade Christmas gift.

Today it’s our own Katie’s turn. Her gift is a simplified version of a kumihimo, a Japanese form of braid.

### Streaming of Maryam Mirzakhani film free until 12th May

Secrets of the Surface is a documentary produced by Zala Films documenting the life and work of mathematician Maryam Mirzakhani. They’re collaborating with the May12 Women in Maths initiative to offer individuals and groups the chance to stream the movie for free, between now and May 12 (Women in Mathematics Day, and Mirzakhani’s birthday).

To get access, you need to complete this short form, so they can keep track of who’s watching it and where.

### Matt Parker does BBC GCSE maths revision videos

Stand-up mathematician and friend of the site Matt Parker has produced a set of videos for teacher resource site BBC Teach, aimed at GCSE maths students.

### Zeckendorf cup arithmetic

My 5-minute talk at the big MathsJam conference this weekend was about some stacking cups that my daughter is too young to appreciate. Here’s the really quick version, in just over a minute:

I gave the answer at MathsJam, but the title of this post contains a big hint that should get you there with a bit of googling.