kwa nini kila wakati tunazingatia uso wa kiwango ili kudhibitisha kuwa gradient ni perpendicular hadi vekta ya tangent kwenye uso... vipi ikiwa chembe itasogea kwenye uso ambao haufanyiki. ina thamani ya kudumu kote kikoa cha ufafanuzi####[['uso wa kiwango', 'Mathematical_Related_Concept', 'NEU'], ['gradient', 'Mathematical_Related_Concept', 'NEU'], ['vekta ya tangent', 'Mathematical_Related_Concept', 'NEU'], ['thamani ya kudumu', 'Mathematical_Related_Concept', 'NEU'], ['kikoa cha ufafanuzi', 'Mathematical_Related_Concept', 'NEU'], ['perpendicular', 'Mathematical_Related_Concept', 'NEU']]