A regular pentagon with a diagonal and an extended side. What is the top angle of the isosceles triangle?
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Solution
The angle α is 108°.

Poem
The tympanum found in architecture element
Or in an arch or pediment
But not only
Tympanum is also anatomy
And eardrum in biology
Last but not least a handdrum or timpani
Some buildings have it as religious imagery
You can see a lot of examples
As usually
In my small poetry
