What domain should I choose in order to impress?

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I have to take part at a communications session about maths, where I am supposed to present a piece of theory (about smth in maths like geometry, complex numbers, trigonometry)followed by 1 or 2 comlex exercises about the domain i have chosen. Please send me matterials if you have! I want to impress the jury, everyone, so i need smth interesting! Help me please!!!!!!!