He did not mention that the curvature is the product of the minimum and maximum directions. Otherwise, a fair question would be that the gaussian curvature woul

He did not mention that the curvature is the product of the minimum and maximum directions. Otherwise, a fair question would be that the gaussian curvature would be different depending on how we draw our lines. In the video, he happens to draw one direction along the fold of the paper, which gives the correct answer. Good video though!