Anyone know what the K key does on my Texas Insturments SR-40 (I'ts got an LED display, it 'gots' to be old!) I have googled, I found lots of stuff on a signal processor (?) with that name, and a few pages that show the calculator, and give a date range for Mfg. but nothing that describes the keyboard. I tried pressing the K key in several cases 5 sin = 5 K sin 543 = 54K3 (K does not end a number ) tis a puzzlement. : ^ )