backpropagation sin, polynomial functions

[Amaterasu]

Hello,

I implemented the xor and other binary functions. It was simple you have 2 inputs (1 or 0) and aim the desired function depending on the inputs

for example

{1 1 0
  1 0 1
  0 1 1
  0 0 0
}; for xor

but i am trying to apply the algorithm to some sin(x), f(x) = polynomila function

i normalize the inputs...and then restore them but still it remains in mist
i create an array with random values and result of the function on these values (aim)

{xi , f(xi)}
should i add wrong answers?  like {xi, f(xi)+1}
what exactly learning these fuctions is about, the algorithm saying point(x,y) is correct or incorrect?

Thanks in advance