Compare the accuracy of sinpi(X) vs. sin(X*pi).

Create a vector of values.

X = [0 1/2 1 3/2 2];

Calculate the sine of X*pi using the normal sin function.

Y = sin(X*pi)

Y = 1×5

         0    1.0000    0.0000   -1.0000   -0.0000

The results contain small numerical errors due to the fact that pi is a floating-point approximation of the true value of $\pi$. For instance, Y(3) is not exactly zero even though $\sin \left(\pi \right)=0$.

Y(3)

ans = 1.2246e-16

Use sinpi to calculate the same values. In this case, the results are exact.

Z = sinpi(X)

Z = 1×5

     0     1     0    -1     0

Z(3)

ans = 0