Having seen it written on a blackboard in the Simpsons, I wanted to check if
398712 + 436512 = 447212
thus disproving Fermat’s Last Theorem. My pocket calculator confirmed the expression to be true, but those are big numbers, and the calculator lacks precision.
This seemed like a perfect opportunity to use calc mode.
M-x calc to enter calc mode
First enter the left hand side
3987 <Enter> 12 ^ 4365 <Enter> 12 ^
Both numbers are now there in the stack:
--- Emacs Calculator Mode --- 2: 16134474609751291283496491970515151715346481 1: 47842181739947321332739738982639336181640625
Hit + to add them together. Now to enter the right hand side.
4472 <Enter> 12 ^
Now the left and right sides of the original expression are there in the stack, and you can see that whilst they may be sufficiently equal to fool a pocket calculator, they can’t fool Emacs.
--- Emacs Calculator Mode --- 2: 63976656349698612616236230953154487896987106 1: 63976656348486725806862358322168575784124416
Hit – to see the difference:
d g to group the number, then hit y to yank the number back into the current buffer.
… as I just did there.