The Math Major Vol. 2, No. 10

The Math Major

CSU Fresno Mathematics Department

Vol 2. No. 10

Editor: Dr. Larry Cusick.

Math Club Film Series

The Math Club sponsors a video film showing every other tuesday. Everyone is cordially invited to attend.

Math Field Day Coming

(From Dr. Della Duncan) Looking forward to Spring? Remember that the Annual Math Field Day will once again be held during Vintage Days at CSU-Fresno. On Sat. April 18th high schools throughout the valley will send more that 200 students to participate in this traditional event.

This year students will have the opportunity to compete in three different contests. Two problem solving events allow students to compete as individuals or as pairs. There is also a team event which includes a presentation on this year's topic "Public Key Cryptography".

A highlight for this year is the agreement with Wolfram Research to provide their Math Mobile at this event. They will be offering demonstrations of the latest version of Mathematica.

We will be needing volunteers to help with this project. If you are interested please contact Della Duncan 278-4999 or email.

The Graduate Program at CSUF

(From Dr. Hugo Sun) The math department offers a Master of Arts degree in Mathematics. The Master's degree program is for those students who wish to continue their study of mathematics beyound the undergraduate program. Why should you pursue a Master's degree? For more information on our graduate program, contact the math graduate program advisor Dr. Hugo Sun (Ed.).

Problem Corner

Problem 2.9: The ancient Babylonians used the formula K = (a+c)(b+d)/4 for the area enclosed by a quadrilateral with consecutive side lengths a, b, c, d. Prove that the formula is valid only if the quadrilateral is a rectangle.

Solution to Problem 2.9: (Solution by John Jamison)

Areas are as follows:

C = (1/2) cd sin Z

A = (1/2) ab sin X

B = (1/2) bc sin Y

D = (1/2) ad sin W

So the area of the quadrilateral would be

T = (A+B+C+D)/2

= (ab sin X + bc sin Y + cd sin Z + ad sin W)/4

< (ab + bc + cd + ad)/4

= ((a+c)(b+d))/4,

if any of X, Y, Z, W are less than 90 degrees. Since any non-convex quadrilateral can be replaced by a convex quadrilateral (with larger area) with the same side lengths, the proof is complete.

John Jamison submitted the only correct solution.

New Problem

Problem 2.10: (Due Thursday March 12 by 4 pm) We can write 1 = 1/2 + 1/3 + 1/6. Write 2 as the sum of no more than twelve distinct (no two the same) fractions in the form 1/N where N can be any whole number larger than 1 but less than 30.

Solutions may be delivered to the math department office (for Dr. Cusick) or by e-mail at larryc@csufresno.edu. There is a $75 dollar first prize and a $50 second prize to be awarded at the end of the semester to the student(s) who submit the most correct solutions.