That would only be the case if the faces were different in some way. If the faces of the triangles are the same then you can do a rotation.Lukeje said:Surely it's because they are "equal halves"?AC10 said:"Here are two equal halves of an equilateral triangles. They are the same. Why are they the same?"
Since the triangle is equilateral.
Edit: they're not the same; they would be converted by means of a mirror plane, which means they are enantiomeric (in two dimensions). In three dimensions they would be equivalent.
On topic; its the stupid governments idea of making learning accessible. They are doing it with science too. They reason that because the average person will never again condense an alcohol and an acid that they will get rid of all the practical bits and instead teach people how to understand science in the context of their day to day life i.e political policy and stuff.
I was much happier when maths was just maths!