Derivative of Exponential Function

Theorem:If $$y=e^x\,$$, then $$\frac{dy}{dx}=e^x$$ Proof: Let $$y=e^x\,$$

$$\frac{dy}{dx}=\lim_{h \to 0} \frac{e^{(x+h)}-e^x}{h}$$

$$\frac{dy}{dx}=\lim_{h \to 0} \frac{e^x(e^h-1)}{h}$$

By Definition: $$e$$ is the number such that $$ \lim_{h \to 0} \frac{e^h-1}{h} = 1 $$

Therefore: $$\frac{dy}{dx}=\lim_{h \to 0} e^x \lim_{h \to 0} \frac{e^h - 1}{h} = \lim_{h \to 0} e^x \cdot 1$$

$$\rightarrow \frac{dy}{dx}=e^x$$