Throughout my teaching career I have only ever known teachers to teach alternate, corresponding and co-interior angles with reference to Zs, Fs and Cs. Obviously all teachers have stressed that they need to learn the mathematically correct names but invariably students have found this hard to do which hampers them in the long run. The letters, whilst intended as a scaffold have actually become part of the supporting structure. When they are removed the house falls down. I myself have done this time and time again and found myself frustrated by student’s inability to remember that ‘Z angles are alternate’.
Recently I have moved away from Zs, Fs and Cs completely. I have banned any mention of Fs, Zs and Cs from my classroom and focused more on the correct Mathematical words, their meaning and a slightly more conceptual understanding of why the angles are equal/supplementary. I have stressed that ‘corresponding’ means ‘in the same position’, ‘co-interior’ means ‘inside together’ and alternate means ‘one way and then the other’. I have also tried to encourage students to get a feel for the intuition as to why these angle facts exist- noticing for instance that because corresponding angles are in the same position on two parallel lines they have to be equal- they just couldn’t be anything else. Or that co-interior angles are supplementary because of the fact they combine the fact they know about corresponding angles with the fact that angles on a straight line sum to 180 degrees. Similarly for alternate angles- a combination of corresponding angles and opposite angles.
This is a long term approach. It isn’t quick and easy. It takes time, some well-thought out and clear explanations and a focus on long term improvement rather than rapid progress. However, I find that ultimately it improves student understanding and ability to identify and use the angle rules as well as providing students with an added layer of mathematical rigour.