1. Iibsigu wuxuu u baahan yahay inuu fahmo noocyada tuubooyinka birta: A. Waxaa loo qaybiyaa nooca: birta tolida toosan, birta birta aan fiicnayn, tuubada birta ah ee wareega, iwm. tuubo leydi leh, tuubo elliptical ah, tuubo ellipse fidsan, semicir...
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