# Understanding Electronics Basics #2

Discussion in 'General Electronics Chat' started by cowboybob, Mar 26, 2012.

1. ### Muttley600New Member

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So what do mean when you say differences:
Approx = to
& the exact answer if they are saying the same thing?

2. ### Muttley600New Member

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That's what I meant, I'm getting lost in definitions but it made sense to me, I was pressing 5 (X2 button) *3 on calc

Can see now it is 5 sq *3 = 75 then needs sqrt = answer above

Last edited: Apr 3, 2012
3. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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To mathematicians 3.14159 is not ∏. 3.14159 is good enough for engineers, but not for mathematicians.

Mathematicians don't generally see decimals (e.g. 0.99 ). They have their blinders on. They see 99/100.

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5. ### Muttley600New Member

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So which is right?

6. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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It depends if your an engineer or a mathematician.

7. ### Muttley600New Member

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Neither, I just want to learn electronics, so where does that leave me, surely if EE are using minute numbers they need decimals?
Think I'm prob more confused now than before, sorry, I know you are trying to help me

8. ### Muttley600New Member

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So I'm now on post #12, third link, I'm getting there, it is all leading to knowing what sine/cosine & tangent are/mean

9. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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You ran across the 8√3 when solving for a right triangle relationship of c^2 = a^2 + a^2. We got off on a "tangent" because you had never seen the 8√3 form before. Instead of just concentrating where the 8√3 came from we diverged a bit. In studying right triangles later,you ran into the √3.

The right triangle is fundamental to the relationships of the angles and the sides. It's fundamental to the circle, sine, cosine and tangent functions.

10. ### Muttley600New Member

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Yeah, sorry it's so long winded but I've never done anything like this before, once I have the understanding, things should get easier as I see it accounts for all the measurements, I just want to understand it

Night both

11. ### Muttley600New Member

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Ok, you've probably guessed I'm struggling with this, don't know why as there are pictures? But for all the pictures & sohcahtoa theory, they don't actually put the sine etc to them

Am I right in thinking if we had a sloping bank & i wanted to measure the slope at the bottom of it in degrees:
sine = bottom (ground level)
Cosine = height at back of bank
Tangent = slope

Last edited: Apr 4, 2012
12. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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No:

bottom (ground level)
height at back of bank
sloped line is known as the hypontenuse

Now let's say your looking up a hill and we'll call the bottom angle θb because that's the angle we are interested in in this case. θb = Theta @ bottom

So, if we were interested in that angle θb.
the "bottom" would be known as the "Adjacent side" and the "back" would be known as the "opposite side".

If we were interested in the angle at the top of the hill, call it θt, the meanings of "opposite" and "adjacent" would switch.

Last edited: Apr 4, 2012
13. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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The sine, cosine and tangent is just the ratio of the sides defined by the angle.

14. ### Muttley600New Member

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Now your seeing what I can't relate to, what do you mean by the ratio?
I didn't watch that vid because I thought I missed something because they suddenly added degrees

15. ### Muttley600New Member

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So are you saying I've been trying to relate it to lines & it is giving us......it has to relate to the missing line for the length of it doesn't it? Hence we can calculate degree of slope

Are we saying the same thing in different language here?

O/H = sine, that's right isn't it?

That has to be right, but then how is the length of sine converted to degrees?

Last edited: Apr 4, 2012
16. ### Muttley600New Member

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Doh, it's not the missing line, it both lines divided (corners) ignore me

Last edited: Apr 5, 2012
17. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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sin(θ) = Opposite/Adjacent (Sine = Oscar Had); So it's nothing more than the ratio of the two sides defined by the angle.

If you happen to know the ratio of the two sides, there are inverse finctions called arcsin(), arctan() and arctan() and it can tell you the angle as long as the triangle is a "right triangle" (i.e. has a 90 degree angle)

Last edited: Apr 4, 2012
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18. ### cowboybobWell-Known MemberMost Helpful Member

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Think of the gear ratios in your bike:

For 4[SUP]th[/SUP] gear (and I'm making this up) lets say the gear ratio is 4 to 1, in other words, for one, single rotation of the crankshaft, 4[SUP]th[/SUP] gear transfers 4 rotations to the rear axle.

Another way to state that ratio is by the fraction 4/1 (read it as 4 to 1), or 4, or 400% (all these can be done on the calculator).

At the other end, for 1[SUP]st[/SUP] gear, with a ratio of 1 to 4, it would be the exact opposite (4 rotations of the crank shaft to 1 rotation of the wheel), or a ratio of 1/4, or 0.25, or 25%.

For right triangles, sin(q) = opposite / hypotenuse, or the sine is the ratio of length of the opposite (vertical) leg divided by the length of the hypotenuse (the sloping part).

That "ratio" number (as a decimal) can be converted to an angle between the two lines that composed of the bottom line of the triangle and the hypotenuse, at the point where they meet.

Think I've got this right...

<EDIT> Another thought: A ratio is used to express a difference between two items that are related (gears in a transmission, lines and angles that make up a triangle, people who vote for or against an issue). If there are no difference(s), the ratio is 1; any difference at all and the ratio is either more, or less, than 1.

Last edited: Apr 4, 2012
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19. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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The circumferance of a circle is C = ∏d or Pi * the diameter. Re-writing, ∏ = C/d; the the circumference to the diameter of any circle (Ratio) is the value ∏.

When mixing 1 bag of quickrock (cement) to 1 gallon of water when you set your fence posts. That is a ratio.
1 bag Cement/1 gal water

Mixing oil for a two cycle chain saw or lawn mower might be 50:1; 50 parts gasoline to 1 part oil.

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20. ### Muttley600New Member

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Morning KISS, you not sleeping again? & thanks both for the plain explanation of ratios

I'll watch the next vid & see what I understand, sure there will be more questions, I can see clearly that I'm lacking in quite basic math when I look at sites, I have started another sub folder for definitions just for math as a reminder, this mountain keeps getting higher but the view keeps getting better

21. ### Muttley600New Member

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I've just watched this, the missing bit I couldn't understand how we were getting degrees

which is great, I can move forward again now, what is the manual way to do the same thing?

ok, I finally understand sine/cosine & tangent don't get hopeful though as I still need to relate it link 4 in post #12, but I'm dead chuffed with myself

Honesty is admitting the reality.......I really struggled trying to read the whole story, but by breaking it down & trusting you will show me the next paragraph, I finally absorbed what I needed to, still a long way to go but enjoying it

Going to have a break & cut the lawn now as I feel like I've just overcome a big hurdle

Last edited: Apr 5, 2012