Homework Help v1.3

[Ice(v)an]

I'm having some trouble, finding some sites, that gives information that

relates Binomial Coefficients to statistics or

Pascal Triangle to the fibonacci numbers.

[Magnum]

Pascal Triangle to the fibonacci numbers.
This is a pretty nice site.Fibonacci numbers and the Pascal triangle

[]MpC[hebe]

Originally Posted by Ice(v)an

I'm having some trouble, finding some sites, that gives information that

relates Binomial Coefficients to statistics or

Pascal Triangle to the fibonacci numbers.

Not sure if you still needed help with this, but if you look up the Binomial Theorem in wikipedia, I'm sure you'll find plenty of reason that binomial coefficients are related to statistics.

[DeathGuiseX]

Can someone help me with integration? we have to integrate sin x/ cos x dx, or also written as int. tanx dx.
The only other info the teacher gave us is that int. 1/u du = ln |u| + c and that we are using substitution. This may be a simple integration problem, but I was just introduced to this whole thing.

[ahme]

Just take u = cos x and go from there.
One trick to solve integration in the form of coefficients is to see if the numerator is the denominator's derivative or the denominator's derivative multiplied by a constant.
Well here we have the derivative of cos x which is - sin x. Bingo! blindly take the u = cos x and make the substitution. u = cos x then du = - sin x dx thus sin x / cos x dx = 1 / u . -du

Now, given the hint you instructor gave, it should be very easy to do the integral.

[DeathGuiseX]

^Thanks, i got the answer as -ln |cos x| + c, but someone else said that they got -ln |sec x| + c. I looked it up and found the secant answer, how did you get that?

[Denny Crane]

here is the answer
Integral tan(x)

[ahme]

That goes to the properties of logarithm.
ln x^y = y * ln x
thus, -ln |cos x| = ln | (cos x)^-1 | = ln |sec x|

note that it is positive and not negative if the sec is used

[Jeaxz]

Hey, guys, i was wondering if anyone know any easy autobiography and it has to be short. Cause i only have 5 days to work.

[4thseal]

Don't know your deffinition of short, but here's a pretty short, famous, one that you can do a lot with:

Frederick Douglass: Narrative of the Life of Frederick Douglass, An American Slave

^that's the ebook for Frederick Dougleass' autobiography. It's a good read, so check it out.

Some more information of Frederick Douglass:

Frederick Douglass - Frederick Douglass Biography

[Jeaxz]

yoo, thanks again man. Once again you save me ass. Thanks man apperciate it.

[kafukai]

Originally Posted by DeathGuiseX

2. In which of the following substances is hydrogen bonding present? (can be 2, 3, or all answers) CH3NH2 , HOCl, NCl3, NH4Br

I really want to answer about all of your questions, but my english isn't so good and I'm not know the english terms.

The N(Nitrogen - 3.0),O(Oxygen - 3.5),F(Fluorine - 4.0) elements got the higher electronegativity so they allways(with H) got the biggest and strongest hydrogen bonds(F>O>N).

CH3NH2 - Got hydrogen bonds. Because of the electronegativity of the N.

HOCl - Got hydrogen bonds. The same reason, about the O.

NCl3 - Not got hydrogen bonds. It's a covalentic compound and every covalentic compound got only VDV(Van Der Vals) bonds or covalentic bonds.

NH4Br - Got hydrogen bonds. Because of electronegativity of the N; And also the electronegativity of the Br(2.8) is lower than the N(3.0), N can able to use 5 bonds.

[DeathGuiseX]

Yay! More math.
Evaluate int (cosx + sinx)^2 dx <<----for this, I expanded it and made separated it into three integrals, but I don't know what to do from there.
For what value of k > 0, does int (4kx-5k)dx = k^2 <---I have no idea for this, but I'm trying atm.

[ahme]

The first question:
(cos x + sin x) = cos^2 x + 2 cos x sin x + sin^2 x
Whenever there is sin^2 x or cos^2 x, check if anything can be simplified. Here we have cos^2 x + sin^2 x = 1.
(cos x + sin x)^2 = 1 + 2 cos x sin x
The one can be easily integrated.
2 cos x sin x
Again whenever you have a multiplication of two functions check if one is the derivative of the other or the derivative multiplied by a constant. Luckily, we have sin x and cos x. The cos x is the derivative of sin x. So make the substitution u = sin x. Note: you could also have made the substitution u = cos x since the derivative of cos x = - sin x). Now, everything should be easily integrated.

Also, if you are good in trigonometry, you may notice that 2 cos x sin x = sin 2x and you know that integral of sin 2x dx = -½ cos 2x + C

[ahme]

Regarding the second question, aren't you missing any more details in the question? Something like the limits of the integral.

[Magnum]

I need to write a speech on these 2 topics(3mins each) and I need it real fast before 12:00pm:(.
Pls help
1.Generation gap
2.What is your role in saving the ailing planet.
Or u can at least tell me a good site for speeches
your help will be greatly appreciated.

[DeathGuiseX]

Originally Posted by ahme

Regarding the second question, aren't you missing any more details in the question? Something like the limits of the integral.

Nope, thats all they give in the question. I'll find it out today, don't worry. Thanks for the help on the first one thou.

[gaara of the desert]

This has been a while but I'm quite sure, since k is a value, not a variable:

int (4kx-5k)dx = 4k int (x dx) -5k int (dx)= 4k*1/2 x^2-5kx

2kx^2 -5kx=k^2
2kx^2-5kx-k^2=0 (*)

that's true for x= [5k+-(25k^2 -4*2k*-k^2)^1/2] / (4k)

(in a formula like ax^2+bx+c=0 it is x= [-b+- (b^2-4ac)^1/2]/2a)

=[5k+-(33k)]/4k

=-7 or 38/4

fill these in as x in (*) and see what k is.

[GiantMidget]

I need help with my physics homework, the question is

A pelican is flying along a horizaontal path drops a fish from a height of 5.2m.the fish travels 9.3m horizontally before it hits the water below.

The acceleration is 9.81m/s

a)What was the pelicans intial speed

b)if the pelican was traveling at the same speed,but was only 3.6m above the water, how far would the fish have to travel horizontally before hitting the water below

[o({})o]

Originally Posted by GiantMidget

I need help with my physics homework, the question is

A pelican is flying along a horizaontal path drops a fish from a height of 5.2m.the fish travels 9.3m horizontally before it hits the water below.

The acceleration is 9.81m/s

a)What was the pelicans intial speed

b)if the pelican was traveling at the same speed,but was only 3.6m above the water, how far would the fish have to travel horizontally before hitting the water below

Please keep in mind that I am not claiming to be good at physics.

I'm assuming that you aren't to take drag into account.

a_y = 9.81
v_y = v₀ + 9.81t (We can assume the initial vertical acceleration was 0, so v₀ can be ignored.)
d_y = 4.905t²

You find these equations by integrating: a = vertical acceleration, v = vertical velocity, d = vertical displacement, t = # of seconds since release.

So, vertical position is...

5.2 - 4.905t²

However, we know that this vertical position should be 0 when it hits the water...

5.2 - 4.905t² = 0
-4.905t² = -5.2
t² = 5.2 / 4.905
t = √(5.2 / 4.905)

Thus, √(5.2 / 4.905) seconds pass before the fish hits the water.

If it traveled 9.3m in that time, we have a horizontal displacement calculated as follows...

(Note that this assumes the bird's velocity is constant)

d = 9.3 = v₀ * t + (a / 2) * t²
9.3 = v₀ * √(5.2 / 4.905) + (0 / 2) * (√(5.2 / 4.905))² (We use a = 0 since we assumed the bird's velocity was constant, hence no acceleration.)
9.3 = v₀ * √(5.2 / 4.905) + 0
9.3 / √(5.2 / 4.905) = v₀
d_y = 9.3 / √(5.2 / 4.905) * t

Thus...

v_x = 9.3 / √(5.2 / 4.905)
a_x = 0

Now we've answered part a by finding v_x. Part b is fairly similar but uses the information we just found to go in reverse.