MIAMI — When University of Central Florida junior Nicole Nissim got stumped in trigonometry, she checked out what was showing on YouTube.

Nissim typically scours the video-sharing Web site for clips of bands and comedy skits. But this time she wasn’t there to procrastinate on her homework. It turned out YouTube was also full of math videos. After watching a couple, the psychology major says, she finally understood trig equations and how to make graphs.

“I was able to watch them at my own pace and if I didn’t get a concept, I could easily rewind it,” Nissim says. “It was a lot clearer once I watched the video.”

YouTube is perhaps best known for its cavalcade of homemade performances and TV clips, but many people such as Nissim are turning to it for free tutoring in math, science and other complicated subjects.

Math videos won’t rival the millions of hits garnered by laughing babies, but a YouTube tutorial on calculus integrals has been watched almost 50,000 times in the past year. Others on angular velocity and harmonic motion have gotten more than 10,000 views each.

The videos are appealing for several reasons, says Kim Gregson, an Ithaca College professor of new media. Students come to the videos when they’re ready to study and fully awake — not always the case for 8 a.m. calculus classes. And they can watch the videos as many times as they need until they understand.

Viewer comments reflect that. On tutorials posted to YouTube by the not-for-profit Khan Academy, for example, reactions include: “Now why couldn’t my calc instructor explain it that simply?” and “I was just about to leave my physics course. You saved me.” One viewer went as far as to declare to the man behind the videos: “You are god of mathematics!!!”

What’s creator Salman Khan’s trick? Keeping it simple, he says. He takes a laid-back approach, focuses on a single concept and keeps the videos to a digestible 10 minutes. He says he purposely did not create clips featuring himself standing at a whiteboard. He wanted something more akin to sitting next to someone and working out a problem on a sheet of paper. He uses the low-tech Microsoft Paint sketching software, with a black background and brightly colored lines and equations as he works through his explanations.

“If you’re watching a guy do a problem (while) thinking out loud, I think people find that more valuable and not as daunting,” says Khan, a California hedge fund manager by day and math geek by night.

Educated at Harvard and the Massachusetts Institute of Technology, Khan developed his tutoring hobby when a younger cousin was having trouble with sixth-grade math. As word of his knack for teaching spread among relatives and family friends, Khan got tired of explaining the same things over and over, so he created videos and posted them on YouTube. He formed the Khan Academy, currently a one-man show, with the long-term goal of starting a school that uses technology to customize learning for students.

Khan’s video clips have developed a following far beyond that immediate circle of relatives and friends, and now he gets dozens of e-mails a week from around the world — including requests for videos on specific topics and help solving particular problems. He now claims about 600 videos on subjects spanning math, physics and even the tanking economy.