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## 'Pericut' printed from http://nrich.maths.org/

Why use this problem?

The problem offers the opportunity to make a conjecture about how
the two perimeter lengths change and then for learners to try to
prove their own conjetures.

The problem offers a non standard application of the use of the
formula for arc length and an application of one of the main circle
theorems.

Possible approach

Suggest learners experiment with the interactivity and make their
own conjectures.

Key question

If the moving line turns through an angle, what is the connection
between this angle and the changes in arc lengths on either side of
the moving line?