His first contention was not disproved until the 15th century, but his second was disposed of by Abul Wefa (940-998), who succeeded in solving the forms x 4 =a and x4-%ax3=b.
When the river has risen 20 or 21 ft., he proclaims the Wefa en-Nil, Completion or Abundance of the Nile.
This latter problem received the attention of the Arabian astronomer Abul Wefa (loth century A.D.), who solved it with a single opening of the compasses.
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