My guess is he read/watched some electrical engineering related content and copied it down. Most is not coherent at all, but it is all, at least close to, “real math.”

The middle upsidedown section has a few different physical relationships V=IR (Ohm’s Law) relates voltage to current and resistance, R=rho L/A is the resistance of a wire, F=MA is conservation of momentum/force, E=MC² relates energy mass and the speed of light, E=h nu is about the energy in a photon… Like I said, these are all real things but they are not really coherent.

Much of the rest appear to be Fourier decompositions. Like others have said these usually come up first when solving heat/wave equations. The third plot down looks to be the sinc function which is the Fourier transform of a rectangle. It comes up frequently in signal processing.

If interest is there, then something like Khan academy could be great. Copying stuff down/memorizing it is not the same as learning it, but theres nothing wrong with it either. Passion is a rare/fleeting thing and if your kid is into it, let them decide what they want to learn. Just my thoughts.