I was on the train, studying some geometry – the geometry of the sphere – and was considering a result about the area of a triangle on a sphere. The material compared the area of the triangle with the area of the sphere as whole. At which point it occurred to me that I didn’t have the formula for the surface area of a sphere at my fingertips.
When I did O level and A level maths – back in the 70s – I did them in such a way that results, methods, formulae became part of my DNA. So much so that even after a 21-year gap (1981 to 2002) they hadn’t deserted me. I suppose I didn’t do much geometry then – less on surfaces. So while I can rattle off the circumference of a circle, the area of a circle, or the volume of a sphere – its surface area is more elusive.
I have been informed of the formula. As you would expect it involves pi and the square of the radius – but I can’t help thinking that here is something I never actually knew in the first place…
Peter, his blog 