Poor LaTeX in Appendix C (Interpolation)

The math formulas in Appendix C should use normal juxtaposition for multiplication, not `*`. And they should use `\sin`, not `sin`, for the sine.

For example

```math
v_t = \frac{\sin(a(1 - t))}{\sin(a)} v_k + s \frac{\sin(at)}{\sin(a)} v_{k+1}
```

not

```math
v_t = \frac{sin(a(1 - t))}{sin(a)} * v_k + s * \frac{sin(at)}{sin(a)} * v_{k+1}
```