code: func (v Vec) ApproxEpsilon(v2 Vec, threshold float64) bool {
  	if !f64.ApproxEpsilon(v.X, v2.X, threshold) {
  		return false
  	}
  	if !f64.ApproxEpsilon(v.Y, v2.Y, threshold) {
  		return false
  	}
  	return true
  }
docs: // ApproxEpsilon reports wether v2 is approximately equal to v, using provided
  // epsilon value.
  //
  // Element-wise approximation uses f64.ApproxEpsilon()