Input sin(0.5,x) for the 0.5th order derivative of sin(x), which is denoted by `sin^((0.5))(x)`.
It is differrent from power of sin(x) as `sin(x)^2`.
sin(0.5,x) can be computed and plot. d(sin(x),x,0.5) computes the 0.5th order derivative of sin(x).
If you want to hold it (not evaluate), use the derivative holder ds(y,x,0.5).

2. Definition and property of Fractional Calculus

3. Difference between Caputo definition and the Riemann-Liouville definition

The Davison-Essex (Caputo) and the Riemann-Liouville definitions are different in the following aspect: in the D-E formula, differentiation is performed first, then integration;
in the R-L formula it is the other way around. The D-E definition implemented, thus, maps constants to zero, imitating integer order differentiation, while the R-L definition does not.
This property of the D-E definition makes it suitable to work with initial value problems for fractional differential equations. So the Caputo definition is used here.