Question

calcule a área da coroa circular da figura r1= 7cm, r2= 4cm

Answer 1

Olá.

$A_{coroa} = A_{R} - A_{r}\\\\ A_{coroa} = 2\Pi R^2 - 2\Pi r^2\\\\ A_{coroa} = 2\Pi 7^2 - 2\Pi 4^2\\\\ A_{coroa} = 2\Pi.49 - 2\Pi.16\\\\ A_{coroa} = 98\Pi - 32\Pi\\\\ A_{coroa} = \Pi (98-32)\\\\ A_{coroa} = 66\Pi cm^2$