Jay's Slide Rules


The Sine of 4 Degrees

The following is a true story.

In my cubical at work I have a Post 1460 displayed on top of a file cabinet. It has been the topic of a few conversations. We all know the lines: "I remember...", "I used one of those in school...", "What is that?". But I digress.

Yesterday at work, a co-worker in back of me walked around to the co-worker in the facing cubical. He was working on a project. The details of which are not important to this story.

As he was walking to the second co-worker's cubical, he was asking the question "Mike, you have an scientific calculator, right? Do you know what the sine of 4 degrees is?"

Fourteen and a half milliseconds later my mind goes 'click'!! A light went on. I can find that answer on my slide rule. I jumped up, grabbed the 1460, flipped it over to the side that has the trig scales. The gears were turning, after all it has been 25 years since I have had to do a trig calculation on the slide rule.

I was thinking of the basics of trig.
"...the sine of an angle is going to be between 0 and 1."
"...4 degrees is less than 5.7 were the scales wrap, so the value is going to be less than 0.1".
"There it is, 4 degrees. Moooove the hairline to the 4. Read the value on the C scale. Three digits. ...6....9...7."

I then shouted out, "Zero six nine seven." The first co-worker wrote down on his note pad, ".0697".

Mike was still in the process of looking for his calculator. "Oh here it is." He had to turn it on. After a few unsuccessful attempts at determining the sine of 4, he decided that maybe he should refer to the maunal. Time wasted. But he had to dig up the manual. The clock was ticking. "Where, ... oh check the index. Here it is, page (whatever)." Tick, tick, tick.

"Press 4, ... then SIN".

"Oh press EQUAL".

There in the display was the value of 0.069756474.

I was ecstatic!

Here it took my co-worker 3 to 4 minutes on a TI 85 calculator to determine the sine of 4 degrees and I was able to give them the answer in about 5 seconds. Even after almost 25 years, I was able to determine the value in just a matter of seconds.

This REALLY made my day.

Jay Francis


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