c)
[tex]1) \\r^2+21^2=29^2\\r^2=29^2-21^2\\r^2=841-441\\r^2=400\\r = \sqrt{400}\\r = 20dm[/tex]
[tex]2) \\l = 2\pi r\\l = 2\pi*20\\l = 40\pi dm[/tex]
3)
[tex]P = \pi r^2\\P = \pi * 20^2\\P = 400\pi dm^2[/tex]
