So, which is is same as is and therefore, ddk at k0 is going to be at k0 which is , which is same as , which is same as the particle velocity.
కాబట్టి, == మరియు అందువలన, k0 వద్ద k0 , = ఉంటుంది. ఇది = , ఇది కణ వెలాసిటీ తో సమానంగా ఉంటుంది.