code: func isPointAtInfinityNISTP(x, y *big.Int) bool {
  	return x.Sign() == 0 && y.Sign() == 0
  }
docs: // Returns true iff the point (x,y) on NIST P-256, NIST P-384 or NIST P-521 is
  // the point at infinity. These curves all have the same point at infinity
  // (0,0). This function must ONLY be used on points on curves verified to have
  // (0,0) as their point at infinity.