I came across the following sentence in Wikipedia:
The bitangent lines can be constructed either by constructing the homothetic centers, as described at that article, and then constructing the tangent lines through the homothetic center that is tangent to one circle, by one of the methods described above. The resulting line will then be tangent to the other circle as well. Alternatively, the tangent lines and tangent points can be constructed more directly, as detailed below.
It took me a while to parse it because I was hopelessly looking for the missing or. Leaving alone the fact that this passage is clumsy, is it grammatical according to the rules of standard English?
Best Answer
In my view it certainly isn't.
The first sentence doesn't make sense because, as you point out, it uses 'either' without 'or'.
In order to make the whole piece grammatical the writer simply needs to leave out the 'either' (except they may have too many 'constructed/constructings').