# Sam Hartburn

sam@samhartburn.co.uk

# Tag: Geogebra

• ## Excircles and excentres

The incircle of a triangle is fairly well known as the circle inscribed in the triangle – it’s tangent to each of the three sides, which means that it touches each one but doesn’t cross any of them. But did you know that triangles have three more circles that are (sort of) tangent to all…

• ## The Nine Point Centre

How many centres do you think a triangle has? There are more than you might think. Maybe you learned about a few at school – the centroid, incentre and circumcentre are the classic ones that most people learn. But there are a few (actually, more than a few) more than that.

• ## Is a Shape With 1000 Sides the Same as a Circle?

I recently found out about a shape I’d never heard of before: a chiliagon.

• ## #DigitalGeometrySketchbook Days 21 to 30

Throughout the month of June 2021 I created a daily maths art piece, each one using different software or different techniques, as part of the #GeometrySketchbook challenge on Twitter. As mine was all digital artwork, I used the #DigitalGeometrySketchbook tag. Here are the results of days 21 to 30.

• ## #DigitalGeometrySketchbook Days 11 to 20

Throughout the month of June 2021 I created a daily maths art piece, each one using different software or different techniques, as part of the #GeometrySketchbook challenge on Twitter. As mine was all digital artwork, I used the #DigitalGeometrySketchbook tag. Here are the results of days 11 to 20.

• ## #DigitalGeometrySketchbook Days 1 to 10

Throughout the month of June 2021 I created a daily maths art piece, each one using different software or different techniques, as part of the #GeometrySketchbook challenge on Twitter. As mine was all digital artwork, I used the #DigitalGeometrySketchbook tag. Here are the results of days 1 to 10.

• ## Dancing Triangles: Sunday Maths Animations Week 9

A spiral of dancing trianglesâ€¦just because.

• ## Pythagorean Spiral meets Pursuit Curves: Sunday Maths Animations Week 8

Earlier this week I was proofreading a book that mentioned Pythagorean spirals. I had seen them before but never thought about them too deeply, so I gave them a try in GeoGebra. I filled them in with curves of pursuit, just for fun!

• ## More Cardioid Rainbows: Sunday Maths Animations Week 7

Week 7 of my Sunday Maths Animations is another one that started out as a cardioid. Varying a different parameter gives a completely different effect.

• ## Cardioid Rainbow: Sunday Maths Animations Week 6

Week 6 of my Sunday Maths Animations started out as a cardioid, but quickly became something else.

• ## Pythagorean Tree: Sunday Maths Animations Week 5

Week 5 of my Sunday Maths Animations is a Pythagorean tree, drawn point by point.

• ## Rhodonea Spheres: Sunday Maths Animations Week 4

Week 4 of my Sunday Maths Animations is my old favourite the Rhodonea curve, rendered with spheres. The ending is extremely satisfying!