INVERSE PRINCIPALLY CENTROGONAL MATRICES

LeRoy B. Beasley1, Sang-Gu Lee2 §, Han-Guk Seol3

1Department of Mathematics and Statistics
Utah State University
Logan, UT 84322-3900, USA
e-mail: lbeasley@math.usu.edu
2,3Department of Mathematics
College of Science
Sung Kyun Kwan University
Suwon 440-740, SOUTH KOREA
2e-mail: sglee@math.skku.ac.kr
3e-mail: shk@math.skku.ac.kr
Abstract: A real nonsingular n × n matrix A = (aij) is called centrogonal if
A−1 = (an+1−i,n+1−j), it is called principally centrogonal if all leading principal
submatrices of A are centrogonal, and it is called inverse principally centrogonal
if A−1 is principally centrogonal. We give a necessary and sufficient condition
for a principally centrogonal matrix to be an inverse principally centrogonal
matrix.

27 Tips for Parent Conferences

Invite both parents. Encourage both parents to attend conferences when possible. Misunderstandings are less common if both parents hear what you have to say, and you'll be able to gauge the kind of support both parents give the child. (Of course, remember that both mother and father may not be available. Today, when some 60 percent of adult women work outside the home, it may not always be the mother who's available to meet. And many children come from single-parent homes; you could unwittingly hurt a child's feelings by always asking to meet the "mother.")

Make contact early. You'll get your relationship with parents off to a good start if you contact them early in the year, perhaps with a memo or newsletter sent home to all pupils. Give parents an outline of what their children will be studying, and let them know you'll be happy to meet with them during the year. (Be sure to say how and when they may contact you for conferences.)