FullForm[Subscript[Ι,0] ]

Subscript[Ι,0]

Subscript[Ι,0]

FullForm[OverVector[ μ ]]

OverVector[ μ ]

Graphics[{Arrow[{{0, 0}, {0, 5}}], Line[{{0, -1}, {5, 4}}],Point[{5, 4}], Text[Subscript[x, 0], {0, -0.1}], Text[Subscript[t, r], {0, -0.9}],Text["x", {5, 4.2}]}]