Technically to do the same as the pocket calculators you'll need to convert each function in between to radian operation, not only first and last one (easy trap, I went for it as well, see above).
Also it would be interesting to see what is I1-9 or even better (I1-9)*100000000 for example to see if anything hides behind 9.0000...
Open question: anyone knows some "pocket calculator" where you can set higher precision for this kind of operations? And I mean larger than the usual 8-20 digits, maybe 50-100, or even much more. This isn't a really challenging task in itself assuming you have reasonable RAM (and by that I mean even 1-2MB would be plenty), probably the hard part is the user interface itself.
And this can have (somehow) practical applications... for example:
http://what-if.xkcd.com/20/At some point the damn cat steps on the keyboard ... and we start with a speed of 0.9999999999999999999999951c (that is almost c, speed of light, max speed permitted in this universe). You just can't do 1-0.9999999999999999999999951^2 (for example) on any calculator I know of (or I don't know how). And you might need precisely this speed squared, it is something that comes up immediately in this context.
Of course you can do it on paper "old style" like you transform your number in something like (1-49/10^25) and then you do by hand (1-49/10^25)^2. But sometimes you have stuff that doesn't play that nice or you just want to do the calculation and get the result without any tricks.
So, is there any pocket calculator that can do 1-0.9999999999999999999999951^2 with some reasonable precision ?