Slide Rule CF/DF and CI scales

[@sliderulesandmathematics9232]

Note, this is a revision of an earlier video incorporating the virtual slide rule. I just thought it had better clarity and was more concise.

[@martinfiedler4317]

You are great! Here you answer the question that your last vid raised for me: How using the folded scale work. So when I go to CF, I simply put its index on 4 * Pi. Going to 6 on CF I get 4 * Pi / 6. And when I look back to D, I divide by Pi to get the result of 4 * 6. Ingeniously simple actually...

[@sliderulesandmathematics9232]

it really is, and a great tool to teach folks how to visualize numbers and relationships between them. That is why I have a 7 foot long N-500. For teaching logs and trig.

[@JohnLeePettimoreIII]

when i was first learning how to use a slide rule, the inverted scales were the most difficult for me to fully grasp. i could wrap my head around the concept just fine. but the practical use of the scales in calculations gave me fits. even now, when i need to use the inverted scales i have to briefly shut my eyes, take a breath and think to myself, *_"You got this, buddy."_*

[@sliderulesandmathematics9232]

When I look at an equation the first thing I do is say to myself, 'math problem, who's your daddy'. Then I take it down as easily as taking down a flerf that can't see the curve.

[@sliderulesandmathematics9232]

Which scale you use is like a golfer seeing the line on a putt. It takes experience but it just jumps out at you after awhile.

[@erwanthomas]

hello, there is something that I don't grasp. lets call C and D adjacent (because they touch each other) same for CF and DF and D and CF opposite, same for C and DF. if I set the index of C over 2 on D ( adajcent) I can read the result of any calculation on the adjacent scale so I can pick any number on C get the result on D or pick a number on CF and read the result on DF. but if I take the index from the opposite scale meaning align 2 from D with 1 from CF i will read the result on the opposite scale but only for numbers from CF, numbers from C won't work with DF, Why is that? Why is it not symetric?

[@sliderulesandmathematics9232]

Good question let me have a look

[@sliderulesandmathematics9232]

Ok now that I’m not driving and can see exactly what your question is… when you align the index of c you are keying it to the index of cf. If you go from d to cf you are keying to pi on d. As a result you get 6.28 on d

[@erwanthomas]

@@sliderulesandmathematics9232 sorry for my poor english but that's not it. if I want to multiply by 2 I can align 1 on C with 2 on D then when I read 2 on C I can read 4 on D or I can read 8 on CF and read 16 on DF. or I can align 1 on CF with 2 on DF then if I read 4 on CF it gives me 8 on DF and if I read 3 on C I can read 6 on D. if the index is adjacent I can use both scales. now if I align 1 on CF with 2 on D if I read 2 on CF i can read 4 on D but if i read 4 on C i read under 7,9 on DF; if I read 2 on C I get 3,96 on DF

[@sliderulesandmathematics9232]

@@erwanthomas with 1 on c and 2 on d I don't read 8 or 16 on cf/df. With 1 on cf and 2 on df it is correct to read 4/8 on cf/df. I am not getting the values you state when going across scales. I think you may be confusing the scales and misreading them.

[@erwanthomas]

@@sliderulesandmathematics9232 I've check on a decilon and an hemmi 260. If I put 1 on c and 2 on D, c goes from 1 to five (2x5=10) above 1 on c you have PI on CF and 2PI on df and CF goes up to 10xPI/2 and give you 10xPI the decilon goes up to 16 on CF because DF goes up to 3*2. so 8 on CF is above 5,1 on D and gives 1,6 on DF . which is expected because that's what folded scales are for. extend c and D witout having to move the slide too much. it's when you put 1 from CF with 2 on D that only numbers from CF give you the right answer on D but not from C to DF. that's where lies the mystery.

[@barryporter6993]

my head hurts :):). But I think I understand :)Thanks

[@thechef7022]

I'm 14, I'm bored at class and I wanna have some fun, thanks.