Geometria, aiuto!

Ex 144

2·pi·r + 4·r 

per r=12 cm:

2·pi·12 + 4·12 = (24·pi + 48 ) cm=123.398 cm

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pi·r^2 + (2·r)^2

pi·12^2 + (2·12)^2= (144·pi + 576) cm^2=1028.389 cm^2

EX 145

2·pi·r/2 + 2·pi·(r/2) 

r=14 cm

2·pi·14/2 + 2·pi·(14/2) = 28·pi cm

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pi·r^2/2

r = 14 cm

pi·14^2/2 = 98·pi cm^2

144)

Perimetro:

$\small 2p= 2·2r+2·r\pi$

$\small 2p= 4×12+2×12\pi$

$\small 2p= 48+24\pi \approx{123,4}\,cm;$

area:

$\small A= 2r·2r+r^2\pi$

$\small A= 2×12×2×12+12^2\pi$

$\small A= 48×48+144\pi$

$\small A= 576+144\pi \approx{1028,39}\,cm^2.$

145)

Perimetro:

$\small 2p= \dfrac{14\pi}{2}+\dfrac{14\pi}{2}+2×\dfrac{14\pi}{2}$

$\small 2p= \dfrac{\cancel{14}^7\pi}{\cancel2_1}+\dfrac{\cancel{14}^7\pi}{\cancel2_1}+\cancel2×\dfrac{14\pi}{\cancel2}$

$\small 2p= 7\pi+7\pi+14\pi = 28\pi\,cm;$

area:

$\small A= \dfrac{d^2\pi}{2}$

$\small A= \dfrac{14^2\pi}{2}$

$\small A= \dfrac{\cancel{196}^{98}\pi}{\cancel2_1} = 98\pi\,cm^2.$