"Addition" part:
"mutally orthoganl vectors" -> "mutually orthogonal vectors"
"The magnitude of a vector can be found with::" -> "The magnitude of a vector can be found with:"
"Derivatives of vectors" part:
"Here, we have benefitted from the fact that..." -> "Here, we have benefited from the fact that"
"Addition" part: "mutally orthoganl vectors" -> "mutually orthogonal vectors" "The magnitude of a vector can be found with::" -> "The magnitude of a vector can be found with:"
"Derivatives of vectors" part: "Here, we have benefitted from the fact that..." -> "Here, we have benefited from the fact that"