# December 2015 archive

Dec 31 2015

## Modular Subtraction Rule Proof

I’ve already presented and proved the rule for modular addition, so for a sense of completeness, but mostly to satisfy my OCD, now I’ll cover the rule for modular subtraction. When doing subtraction in modular arithmetic, the rule is: If we subtract integer from integer and calculate the difference modulo , we get the same answer …

Dec 31 2015

## Modular Addition Rule Proof

Addition in modular arithmetic is much simpler than it would first appear thanks to the following rule: This says that if we are adding two integers and and then calculating their sum modulo , the answer is the same as if we added modulo to modulo and then calculated that sum modulo . Note that …

Dec 29 2015

## BigDog Has Been Put Down

At 70 robot dog years-old – that’s 10 in human years – BigDog should’ve had a few more years of happily serving his masters ahead of him. Instead, the US Marines have pulled an Old Yeller on the unsuspecting robocanine, sending him to an early grave, or junkyard as the case may be. Created in 2005, BigDog was the result …

Dec 27 2015

## Unboxing Dot, the Brains of a Robot

I’m almost ashamed to admit it, but my daughter got a robot for Christmas, and I had absolutely nothing to do with it. As a matter of fact, I was totally unfamiliar with Dot,  the cute, roughly 3.5 inch, sensor-packed, “brains of a robot” by San Mateo-based Wonder Workshop,  Inc. Now that I’ve had some …

Dec 24 2015

Dec 23 2015

Dec 22 2015

Dec 21 2015

Dec 20 2015

Dec 19 2015