I'm having trouble understanding where exactly the "high frequency masquerading as a low frequency" phenomena is occurring here- if you go from left to right, you're still seeing a step function right? it's just in different spots?
I am having the same problem. How can we interpret high frequencies and low frequencies from images? How does this example demonstrate a high frequency being aliased?
Great questions - the edges of the continuous triangle are in effect perfect step functions, or an infinitely high frequency function, which requires infinitely many kinds of frequencies to reconstruct. Thus, there's no perfect way of reproducing the nice edges in any discrete display or system, and can only approximate them with low frequency components.