In the depths of Pornhub, buried beneath a mountain of hardcore erotica, a 34-year-old Taiwanese man named Changhsu (張旭) taps away at a green chalkboard while speaking a steady stream of Mandarin. In nearly all of his 226 videos, he wears a gray hoodie and black-rimmed glasses, and he never once does anything even remotely pornographic — no blow jobs, no 69s, no anal. He’s on Pornhub for a different reason: To teach calculus. From The Determined Math Tutor Teaching Calculus on Pornhub [Mel Magazine] [CW: calculus]