The math help thread - Printable Version

The math help thread - Printable Version

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The math help thread - apathy - 2009-10-03

Get the expression for your max moment in terms of d and g for θ = 25°. Maximum load is a function of θ, but max moment, d, and g are constants with respect to θ.

Spoiler

The math help thread - Tempus - 2009-10-03

Thank you, I understand what the question means now. The maximum moment is the same always (5000gdcos[25]), so as one of the variables changes (angle/max load), so must the other to get the same moment. I had no idea that that was what the question was telling me, lol.

The math help thread - holyforest - 2009-10-03

Ok, I'm usually able to do problems like this, but I'm suffering from a cold right now and I'm tired and can't think to well. These are two Algebra 2 questions I can't solve:

1) State one solution to the system
y< 2x-1
y> or = 10-x (greater than or equal to)

2) Write a system of inequalities whose solution is the set of all points in quadrant 1 not including the axes.

>_> Any help would be appreciated.

The math help thread - Tempus - 2009-10-04

holyforest Wrote:1) State one solution to the system
y< 2x-1
y> or = 10-x (greater than or equal to)

Either 1) plot the graphs to find the region which satisfies the equations or 2) re-write them like so:

$[Image: eq.latex?2x-1%3Ey\ge%2010-x]$

$[Image: eq.latex?3x-11%3E0]$

$[Image: eq.latex?x%3E\frac%7B11%7D%7B3%7D]$

So let's say that $[Image: eq.latex?x=4]$ .

$[Image: eq.latex?2(4)-1%3Ey\ge%2010-4]$

$[Image: eq.latex?7%3Ey\ge%206]$

So let's say that $[Image: eq.latex?y=6]$

That's one example.

holyforest Wrote:2) Write a system of inequalities whose solution is the set of all points in quadrant 1 not including the axes.

Well the first quadrant is the one where all points are positive or 0. Since it says DON'T include the axes, we define x and y to be positive, but more than 0:

$[Image: eq.latex?x%3E0]$

$[Image: eq.latex?y%3E0]$

And there's your system of inequalities.

The math help thread - Cursayer - 2009-10-06

My math teacher told me to find all digits of pi. (Yes, I'm serious.) Where can I find this?

The math help thread - KajitiSouls - 2009-10-06

Cursayer Wrote:My math teacher told me to find all digits of pi. (Yes, I'm serious.) Where can I find this?

Taylor Series. I hate those >_>
$[Image: c3a379aaf2b04999084373279ed2da10.png]$

Set the equation to cos(x) = π, then start chugging away at the summation sequence. The further you go, the more digits of pi you'll get!

(wow w/e default language sp.net uses, it's raping Pi)

The math help thread - Russt - 2009-10-06

Cursayer Wrote:My math teacher told me to find all digits of pi. (Yes, I'm serious.) Where can I find this?

There are two: p and i. Biggrin

Alternatively: http://www.angio.net/pi/piquery

But yeah, if you were to compute pi, you'd use a Taylor series as Kajiti mentions or some other method that converges to it. I know Wikipedia has a whole list of them.

The math help thread - Nikkey - 2009-10-06

Cursayer Wrote:My math teacher told me to find all digits of pi. (Yes, I'm serious.) Where can I find this?

You cannot find all digits of pi. pi is irrational.

The math help thread - sky54264 - 2009-10-06

Devil's Sunrise Wrote:You cannot find all digits of pi. pi is irrational.

His teacher is irrational.

The math help thread - KajitiSouls - 2009-10-07

Devil's Sunrise Wrote:You cannot find all digits of pi. pi is irrational.

Doesn't stop one from trying Stunned

Case in point, people holding memory contests on the digits of pi. The winner got up to like 5 million digits or something. Somehow that almost seems like 1 gig of RAM o.O

Also, it's probably better to describe pi as transcendental, since by definition transcendental numbers, in addition to certain properties, are also irrational ones.

The math help thread - Nikkey - 2009-10-07

^ True, true.

(The thing is, most people know what irrational numbers are. Not everyone I know know what transcendental numbers are, for example.)

The math help thread - KajitiSouls - 2009-10-07

Devil's Sunrise Wrote:^ True, true.

(The thing is, most people know what irrational numbers are. Not everyone I know know what transcendental numbers are, for example.)

I knew that irrational numbers cannot be described by simple fractions, but I didn't know about the "cannot be represented as a decimal" part either. I always associated transcendental numbers with that latter part xD

Here's a problem...
[FLEFT] [Image: proglem.jpg]

[/FLEFT] In the setup shown, S is a length of cord 30'' long, and L is a rod of 20'' long. L also weighs 10 pounds. The whole entire system next to the wall is at rest.

Find the tension in S and the length h.

This is seriously all that is given.

.

The math help thread - Nikkey - 2009-10-07

KajitiSouls Wrote:I knew that irrational numbers cannot be described by simple fractions, but I didn't know about the "cannot be represented as a decimal" part either. I always associated transcendental numbers with that latter part xD

Well, there's always a digit after the "last" digit, else this theory would apply:

[Image: yb8ruhz.png]

And then pi would be rational!

But yeah, pi can't be described as a root of anything either, and that's a special thing.

The math help thread - Corn - 2009-10-08

Hi I'm doing Trig.

Anyways, this problem says to simplify

(sec x) (cox x + sin x squared * sec x)

in terms of cos x.

I got 2 - cos x squared, but the book says

1 / cos x squared.

What do you guys get? =/

The math help thread - Biotype - 2009-10-08

ClawofBeta Wrote:Hi I'm doing Trig.

Anyways, this problem says to simplify

(sec x) (cox x + sin x squared * sec x)

in terms of cos x.

I got 2 - cos x squared, but the book says

1 / cos x squared.

What do you guys get? =/

I find it easiest to change the sec x's to 1/cos x's. After that, just simplify by adding what's in the parenthesis (remember (sinx)^2 + (cosx)^2 = 1) and multiplying by the outer 1/cosx.

Parenthesis overload

The math help thread - KajitiSouls - 2009-10-08

Remember the trig identity sin(x)^2 + cos(x)^2 = 1?

Divide the whole thing by cos(x)^2, and you get a new trig identity!

tan(x)^2 + 1 = sec(x)^2 = 1 / cos(x)^2

(in case you didn't know, ^ means "to the power of")

Also... no one can help me on my problem?

The math help thread - Tempus - 2009-10-08

I attempted it, and I "think" that I managed to get h in terms of one of the angles (the upper-right one), but I also managed to get the upper-right angle to be 0. So I'm gonna say that my first attempt failed miserably, lol.

The math help thread - XTOTHEL - 2009-10-08

Tempus Wrote:I attempted it, and I "think" that I managed to get h in terms of one of the angles (the upper-right one), but I also managed to get the upper-right angle to be 0. So I'm gonna say that my first attempt failed miserably, lol.

You can't solve for h simply because you need more info. Unless somewhere in the diagram or something says to assume that the rod is perpendicular with the wall.

The math help thread - Tempus - 2009-10-08

XTOTHEL Wrote:You can't solve for h simply because you need more info. Unless somewhere in the diagram or something says to assume that the rod is perpendicular with the wall.

If I write the 3 angles of the triangle as a, b and c, I can get h and T in terms of a, b and c via moments. I can't solve to get h yet, but I thought I had an equation for it that would work.

The math help thread - KajitiSouls - 2009-10-08

Oshiet, I think I figured it out!

The key word is that the whole system is in equilibrium. That means all forces acting on the system (cord, rod, and wall) should intersect at one point. If that wasn't the case, there would probably be momentum left over. Taking this information, we deduce that the point of intersection is in the middle of the length of cord, which means that the bottom-most part of the system is also h distance away from where the rod is touching the wall.

h = 12.###

Wow, statics seems so much easier now lmao >.< Finding the tension in S is trivial after knowing h.