the old aunt (tan opp/adj) sat on her (sin opp/hyp) coat and hat (cos adj/hyp) the trig is ok for theoretical, but in practical values the wall can only adjust by a course of bricks either above or below the theoretical. It depends on what you are building. for a bog standard back of the yard shed I would keep the scale to sizes that can be easily bought. ie front height less than 2.4 metres and rear 2.1 to allow some head room. There is always waste, and cutting off a little from a standard size is usually less costly than having to buy more for a larger size.