Two equilateral triangles are constructed such that they share a side with a third triangle as shown.

Find the value of the angle coloured red

This problem is from the excellent book Geometry Snacks by and reproduced here with permission. (c) 2017 Ed Southall and Vincent Pantaloni https://www.tarquingroup.com/geometric-snacks.html

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*"Hi John, brill web site. However I really have no clue at all about Geometry Snacks which you downloaded from the book. At what level do you think this would be appropriate?
[Transum: Thanks. I think it would be appropriate for A Level, IB students or to really challenge Higher GCSE students.]"*

*Tracey Peto,
Friday, August 2, 2019*

How did you use this starter? Can you suggest how teachers could present or develop this resource? Do you have any comments? It is always useful to receive feedback and helps make this free resource even more useful for Maths teachers anywhere in the world. Click here to enter your comments.

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