Incorrect notation on example

[mlxd]

Describe the bug
The example at https://ichec.github.io/QNLP/examples/gate_ops/ has a mistake in notation for S4 and S_i at the end of page.

Expected behavior
Si=σxRY(cos−1((i−2)/2)))σx and Si=RY(−cos−1((i−2)/2))) should be Si=σxRY(cos−1((i−2)/i)))σx and Si=RY(−cos−1((i−2)/i))) respectively.