Spoiler for

Triangle formed by centers:

sides: 7 , 8, 9

angles:73,58,48 (using laws)

Area: 26.8328 (Heron's)

Sector areas of circles:

3cm: pi3x3x73/360=5.7334

4cm:pi4x4x58/360=8.0983

5cm:pi5x5x48/360=10.4720

Area of sectors=24.30371

Area between circles is 2.52909

area ( triangle -sectors) formed

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