Dr. Margaret Sloan and Josh Cosby show off the Mathematics Teacher publication featuring “Cosby’s Rule,” which Cosby developed in AP Calculus class. When he was a senior at Washington Wilkes Comprehensive High School, Josh Cosby didn’t set out to formulate a new rule for solving calculus problems. He just saw a logical shortcut to solving them, and now that shortcut has been proven by the experts and published for all math teachers to use.

They call it “Cosby’s Rule.”

To her credit, his AP Calculus teacher, Dr. Margaret H. Sloan, didn’t dismiss the shortcut when she first saw him use it in 2008, and now it’s been published in the August 2010 issue of Mathematics Teacher, the journal for the National Council of Mathematics Teachers.

“Josh didn’t like to do all the computational steps in the calculus problems we were working on, and somehow he saw this shortcut, which I had never seen. The genius part was that he was doing something that we hadn’t even gotten to yet,” she said.

He’d solved several problems with the shortcut, she said, then the rest of the class investigated the shortcut and saw that it would work with all the problems involving summation operations and definite integrals. “They even worked problems they hadn’t been assigned, and saw that it worked every time. We started calling it ‘Cosby’s Rule.’”

To see if the shortcut was simply something she had never come across, Dr. Sloan ran it by math professors at the University of Georgia. “None of them had ever seen this particular shortcut,” she said. “It was so clever, because it cuts out a lot of tedious calculations and saves time.”

With help from one of the professors, Sloan proved the solution and wrote a paper on Cosby’s Rule and submitted it to Mathematics Teacher. “They accepted it for publication immediately,” she said, “but it took two years for them to fit it into their schedule.”

Meanwhile, Josh, the son of David and Betty Cosby, graduated with the class of 2008 and was accepted at Georgia Tech. Now 20, he’s on sabbatical from college but expects to return to school in the spring. “It’s kind of cool to have Cosby’s Rule published,” he said, “but it’s not going to make me a lot of money or anything. I’m just going back to school and take it from there.”