Thread by @Kit_Yates_Maths

For everyone who has been commenting on this thread. Thanks for all you great comments and insights.

The @DailyMirror's @roooooosaleen picked up the story and I gave them her thoughts here:
mirror.co.uk/news/weird-new…

https://twitter.com/Kit_Yates_Maths/status/1364474242088239104

If it's a semi-circle then I think the technical answer is true.
You can define the angle between two non-straight line curves at a point can be defined as the angle between their tangents at that point. If this is a semicircle then these two angles would indeed by 90 degrees.

Some people have pointed out that it might be a different sector of a circle which would make the answer false.
For many students first learning about angles the definition uses the idea of two straight lines meeting at a point in which case the answer would also be false.

It's actually a really thought-provoking question which could be used later on in school to spark conversations about infinity, tangents, calculus and many more interesting mathematical concepts, but it might not be best for seven-year-olds being homeschooled by their parents!

I think the question could have been made unambiguous by using a different figure like a triangle which does not have right angles when drawn in the plane (lets not get into non-Euclidean geometry here).

If you wanted to know what the “official” answer was then someone sent it to me earlier.
This was the sort of answer I eventually guided my daughter to, but we had a good discussion along the way.