They want all of the error to be in the vertical direction. So e.g. sin(x/T) cannot approximate (0,1) in their sense for any T. Similarly, it cannot simultaneously approximate (1,0) and (2,1).
Still doesn’t work. If (xi)3i=1 is an arithmetic progression then (exp(i(axi+b)))3i=1 is a geometric progression, the imaginary part of which is (sin(axi+b))3i=1. This implies that for example sin(ax+b) cannot simultaneously approximate (0,0), (1,0), and (2,1).
They want all of the error to be in the vertical direction. So e.g. sin(x/T) cannot approximate (0,1) in their sense for any T. Similarly, it cannot simultaneously approximate (1,0) and (2,1).
Sorry, we need sin(ax + b).
Still doesn’t work. If (xi)3i=1 is an arithmetic progression then (exp(i(axi+b)))3i=1 is a geometric progression, the imaginary part of which is (sin(axi+b))3i=1. This implies that for example sin(ax+b) cannot simultaneously approximate (0,0), (1,0), and (2,1).