Jefferson High School teacher Paul Oliverio, wearing his "MATH HURTS" T-shirt, gave the signal to hit the boombox sitting at the rear of the classroom.

As the rhythmic rant of a too-cool rapper, backed by pounding bass and drums, began to fill Room 312, smiles crept out on the faces of his captive audience.

But wait--this wasn't Ice Cube, Ice-T or Dr. Dre. This was . . . oh noooo!

"PYTHAGO-RAP!!!"

That's Pythago as in Pythagorean theorem, the ancient, all-important geometric principle about right triangles--and bane of many a modern 10th-grader.

The bigger shock, however, wasn't the message. It was the messenger.

That rapper spitting out lines about "additude," altitude and hypotenuse was none other than Oliverio, a fact that when revealed, caused some students to clutch their chests and gasp, "That was you?"

What possessed this 25-year classroom veteran, known to students and colleagues alike as a stern taskmaster, to hip-hop where few math teachers have dared to venture?

Oliverio does not believe in coddling students. Nor does he think that all good teaching must be swashbuckling entertainment. "My purpose is not to make you feel better," he said. "My purpose is to make you smarter. Because once you're smarter, you're going to feel better."

Nonetheless, he said he sees no harm in making learning fun. Attitude, not aptitude, he believes, is the chief reason many kids perform badly in math.

"I have many examples of gang kids who could just as easily get an F as a B," said the Burbank resident, who has taught at Jefferson, an inner-city Los Angeles school, for nine years. "They get an F, not because they don't understand it, but because they don't want to."

Administrators say he is on the right track.

"In mathematics, young people feel they don't want to be there-- it's boring, they don't see the relevance to their own lives," said Principal Virginia Preciado. "Sometimes we need to be very creative and get kids excited about concepts that seem irrelevant to them. Mr. Oliverio is very excited about getting kids to see mathematics in a fun way."

In Pythago-rap, Oliverio combines the math message with a bit of history, as well as music. The rap leads students through a proof of the Pythagorean theorem discovered by James A. Garfield 120 years ago, shortly before he became the 20th president of the United States.

At a math teachers conference a few years ago, Oliverio heard Glendale College instructor Sidney Kolpas lecture on Garfield's proof, one of more than 350 known validations of the theorem named after an ancient Greek society of philosophers called the Pythagoreans.

The theorem states that the square of the hypotenuse (the side of a right triangle opposite the right angle) equals the sum of the squares of the other two sides.

Over the centuries, mathematicians have devised hundreds of complex proofs of the theorem.

But Garfield, who worked out his proof during a monotonous hearing when he was a member of Congress, found a way to use a single trapezoid to prove that the Pythagoreans were right. His proof, which was published in an 1876 edition of the New England Journal of Education, is considered the simplest and most elegant validation of the geometry rule.

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What lit Oliverio's imagination was learning from the Kolpas lecture that Garfield signed his proof with the initials "JAG MC."

MC stood for member of Congress. But to a member of postmodern American culture, MC means something else altogether: rap music, as in rap master MC Hammer.

"I thought, wouldn't it be great if somebody set this to rap music?" Oliverio recalled saying to Kolpas and the other teachers in the meeting.

Some of them looked at Oliverio as if he had sprouted four heads. Kolpas, himself a rather unconventional teacher--known to sing songs about calculus to his college students--told him to go for it.

"I was half kidding. But I like to encourage colleagues as well as kids to be creative," Kolpas said. "Paul certainly carried it to an extreme."

Inspired, Oliverio sat at his computer past midnight for several weeks crafting the lyrics, then recorded the composition in a friend's garage studio. He has played it for students every year for the last four years.

The rap puns shamelessly--a clue, perhaps, to Oliverio's short-lived past life as a stand-up comic. Right triangles, for instance are

. . . warm triangles

(They won't make you sneeze)

They are from the land of 90 degrees

Self-esteem messages are squeezed in along with the hard-core math.

The area of the whole

Equals the sum of the parts

Look inside the trapezoid

Cuz you got the smarts. . .

At one point, to segue into the nitty-gritty of Garfield's calculations, the rap even borrows from Arsenio Hall, adapting the celebrity's famous fist-waving salute for a chorus of "Proof! Proof! Proof!"

That bit brought down the roof in the eyes of the only critics who mattered.

"It was very cool," said student Rafael Roman. "I thought it was going to be boring, old music. I was surprised, definitely."