$\frac{\partial }{\partial t}(f \circ \phi^{-1} \circ \phi \circ \gamma)(0)=\frac{\partial}{\partial t}(f \circ \psi^{-1} \circ\psi\circ \gamma)(0)$

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enter image description here I feel like this result is in a way obvious, since we can just apply the chain rule several times: \begin{aligned} \frac{d}{dt}(f \circ \phi^{-1} \circ \phi \circ \gamma)(0) &= D_{f\circ\phi^{-1}\circ \phi}(\gamma(0)) \cdot \gamma' (0) \newline &= D_{f\circ(\phi^{-1}\circ \phi)}(p) \cdot \gamma' (0) \newline &=D_f(\phi^{-1}(\phi(p))) \cdot D_{\phi^{-1} \circ {\phi}} (p) \cdot \gamma'(0) \newline &= D_f(p) \cdot D_{id}(p) \cdot \gamma'(0) \end{aligned} where $D$ denotes the Jacobian of the respective function. We can do the same for the expression $\frac{d}{dt}(f \circ \psi^{-1} \circ \psi \circ \gamma)(0)$ and derive the same result.

Is that really it? Did I use somewhere that $f$ is a real valued function? Did I use that $\phi$ and $\psi$ are charts (except for the fact that the expression is well defined since the respective inverse maps exist)?