Sunday
May 29, 2016

Posts by Damon

Total # Posts: 26,282

Science
model ? example Bohr atom ?
January 3, 2016

Calculus
http://mathworld.wolfram.com/Semicircle.html look at integration for weighted mean, then divide by area. pi r^2/2
January 3, 2016

Calculus
4 r/3pi is the semicircle do the outer one, then subtract the inner one. See for example: http://en.wikipedia.org/wiki/List_of_centroids
January 3, 2016

math
(-1)^ even power = 1
January 3, 2016

Math
it is 4, the distance from west 2 to east 2 :)
January 3, 2016

Math
n^2 - 4 = 21 + 9 n n^2 - 9 n -21 = 0 (n-7)(n+3) = 0 n = 7 so the smallest is 5
January 3, 2016

Math
They are POSITIVE, odd numbers are OUT so they differ by TWO n-2 , n , n+2 (n-2)(n+2) = 21 + 9 n
January 3, 2016

math
x^4 - 5 x^3 + 5 x^2 + 4 x - 61 = 0 find the roots try http://www.wolframalpha.com/input/?i=x^4+-+5+x^3+%2B+5+x^2+%2B+4+x+-+61+%3D+0+&x=5&y=5
January 3, 2016

Algebra
55 t +120 - 40 t = 135 15 t = 15 t = 1 hour at 55 so 55 miles on highway 2 hours at 40 = 80 miles on dirt
January 3, 2016

Algebra
55 t + 40 (3-t) = 135
January 3, 2016

math
I will leave you to get s now
January 3, 2016

math
.866 s = 950 sin h - 90 .866 s = 1645 cos h ---------------------subtract 950 sin h = 1645 cos h + 90 or 950 sin h - 1645 cos h = 90 for various values of h h , left side 60 , .224 61 , 33.4 62 , 66.5 63 , 99.6 so steer 62.5 degrees west of south 65 , 165 70 , 331
January 3, 2016

math
He must stay on a course of S 60 W. We must find the heading :) h is degrees heading west of south say his speed over the ground is s then west speed over ground = s sin 60 = 950 sin h - 90 and south speed over ground = s cos 60 = 950 cos h so .866 s = 950 sin h - 90 .5 s = ...
January 3, 2016

Does not make sense
You say Ruth has 130 then ask how much she has.
January 3, 2016

Geography (Ms.Sue ) Help
Interesting - stress seems to lead to more babies. War torn Afganistan is top at 2.4 followed by Maldives threatened by flooding at 1.9 Quiet but lonely Nepal at 1.2 Quiet Sri Lanka (since the tsunami) lowest at 0.8
January 3, 2016

Geography (Ms.Sue ) Help
http://www.google.com/search?q=population+growth+nepal&ie=utf-8&oe=utf-8 http://www.google.com/search?q=population+growth+afganistan&ie=utf-8&oe=utf-8 http://www.google.com/search?q=population+growth+sri+lanka&ie=utf-8&oe=utf-8 http://www.google.com/search?q=population+growth+...
January 3, 2016

math
6-4 5-3 4-2 3-1 4-6 3-5 2-4 1-3 so 8 work out of how many 6 * 6 I think or 36 so I get 8/36 = 2/9 see: http://www.freemathhelp.com/rolling-dice.html
January 3, 2016

physics
Ah, did not think of that :)
January 3, 2016

physics - No way - directions not defined
Is it pushed up or down the slope? Is that 20 m/s up slope or down slope? I will assume both are UP and you will have to get it straight yourself. weight component down slope = m g sin 37 = 80 * 9.81 * sin 37 = 472 N If you are pushing up with 400 N, you lose, at least on ...
January 3, 2016

chemistry
Maybe lea nitrate ?
January 3, 2016

math
a7 = a + d(6) = 21 {so 2a+12 d = 42} sum of first 13 = (13/2)(2a + 12d) = (13/2)(42) = 13 * 21 = 273 look at: http://www.mathsisfun.com/algebra/sequences-sums-arithmetic.html
January 3, 2016

Calculus pz help urgently
-.25 cos (2x-pi/4) - .25 x sqrt 2 + c
January 3, 2016

Calculus pz help urgently
note we no longer have sine curves with zero mean value but now have an average plus a cosine curve with twice the frequency.
January 3, 2016

Calculus pz help urgently
note sin pi/4 = sqrt2/2 -.25 cos (2x-pi/4) - .25 sqrt 2
January 3, 2016

no, wrong
I guess maybe you mean sin x cos(x-pi/4)dx sin x cos y = .5 sin (x+y) + .5 sin (x-y) (remember "beat frequency" ) so .5sin ( 2x-pi/4)dx + .5sin (pi/4)dx
January 3, 2016

Calculus pz help urgently
I guess maybe you mean sin x cos(x-pi/4)dx sin x cos y = .5( sin x +sin y) + .5 (sin x - sin y) (remember "beat frequency" ) so .5(sin x + sin(x-pi/4)dx + .5(sin x - sin(x-pi/4)dx ---------------------------- add (oh my) sin x dx -cos x + c
January 3, 2016

sorry, do not know
As far as I know zero to the anything is zero.
January 3, 2016

Math
You are welcome.
January 3, 2016

Math
a) 2/7 b) 5/7 * 9/24 c) assume 6 am for maximum inconvenience so 8/24
January 3, 2016

math
20/16 divide top and bottom by 4 5/4
January 3, 2016

math
still 5/4
January 3, 2016

Math
c T = wavelength - 3 m (1/4)3 = .75 meters = 750 cm
January 3, 2016

Math
how long would a (1/4) wave antenna be? (use c = 3*10^8 meters/second)
January 3, 2016

math- HELP!
$2600 initial at 8% compounded continuously
January 2, 2016

Do you get it now?
Get the idea? Richer # = log of amplitude. so you take 27 times the antilog and then take the log of that
January 2, 2016

Math Exponetial Function Problem Question?
here slowly Richer number = 3.2 3.2 is log of amplitude A log A = 3.2 10^logA = A = 10^3.2 = 10^3 * 10^.2 so A = 10^3 * 1.5848 Now Multiply THAT by your 27 B = 10^4 * 4.27921 log B = log 4 + log 4.27921 = 4.631 which is your new Richter #
January 2, 2016

Math Exponetial Function Problem Question?
You multiply the 27 by the amplitude, not the log of the amplitude. then take the log of the new bigger amplitude for the new Richter number.
January 2, 2016

Math Exponetial Function Problem Question?
No, log scale I answered this yesterday http://www.jiskha.com/display.cgi?id=1451681946
January 2, 2016

Spanish
whew :)
January 2, 2016

Math
I did this not long ago http://www.jiskha.com/display.cgi?id=1451681946
January 2, 2016

Math
hint here: http://www.jiskha.com/display.cgi?id=1451675195
January 2, 2016

Math
You are welcome.
January 2, 2016

Math
Suspect you mean 2^(2x+3) = 80 that means (2x+3)log 2 = log 80 (2x+3) = 6.32192 2x = 3.32192 x = 1.6609
January 2, 2016

Math
19 * 100 / 27 = 70 % is his score in percent. I do not know if you are using letter grades or whatever.
January 2, 2016

Math
I think your answer is fine. So is the 3^2 = 9 one.
January 2, 2016

Math
well 9^x = 3^(2x) so log^-1 (2 x log 3) is a perfectly good answer. So is Log^-1(xlog(9)) They are the same :)
January 2, 2016

Math
Yes, but count brackets. I try to use different ones log^-1[ x(log 7 - log 8) ]
January 2, 2016

Calculus
It is just that sqrt (a^2-b^2) is not a - b
January 2, 2016

Calculus
By the way, you tried x^3 as well :..... sqrt (1-x^6) into 1^(1/2)- x^(3) ..."
January 2, 2016

Calculus
Why should I not let u = anything I choose ? LOL I see an x^6 and an x^2 so I tried x^3
January 2, 2016

Calculus
sin^-1 u + c so sin^-1 x^3 + c
January 2, 2016

Calculus
sqrt (1-x^6) into 1^(1/2)- x^(3) I do not think so I will try the easy way u = x^3 du = 3 x^2 dx so I have du/ sqrt (1-u^2)
January 2, 2016

Calculus
B and D
January 2, 2016

Calculus
In C, that nasty x cancels
January 2, 2016

Calculus
the problem with B and D is that dx = dy/f(x) so the substitution does not get rid of the x
January 2, 2016

Calculus
I had trouble with B and D
January 2, 2016

Calculus
∫√(x^2-1) dx <---- NOTE that dx let y = x^2-1 then dy = 2 x dx so dx = dy/2x ∫√(x^2-1) DX =∫y^.5 dy/2x a mess again
January 2, 2016

Calculus
You are wrong. A CAN easily be solved Be sure to include the dx in your integrals so you include it when you substitute
January 2, 2016

Calculus
B. let y = 1 - x^2 dy = -2 x dx ∫1/√(1-x^2) dx = ∫y^-.5 dy/(-2x) very awkward Hey be sure to include the dx in your integrals C will be easy because the x in -2xdx cancels
January 2, 2016

Calculus
A. let y = x-1 dy = dx ∫√(x-1) = ∫y^.5 dy that works
January 2, 2016

Calculus
You are welcome.
January 2, 2016

Calculus
∫(x^3-x^2) dx/x^2 =∫(x^3/x^2-x^2/x^2)dx = ∫(x^3/x^2-x^2/x^2)dx = ∫(x-1)dx = (x^2/2) - x + c which is the fourth option and is also what you got
January 2, 2016

spanish
If you are not sure and you are taking Spanish, we have a serious problem here :)
January 2, 2016

spanish
Lives in a hotel and is rich and spends much money Does not respect Mexicans or appreciate their clothes. But, interestingly Peace Corps volunteers must come from a different country entirely :)
January 2, 2016

World Civilizations
Of course there was introducing the natives to Christianity. I do not think I will follow that train of thought further and have deleted a sentence or two.
January 2, 2016

Physics of ice skating
Well, I guess the skate you are pushing with is at an angle so the long sharp edge can get a grip on the ice while the forward skate moves forward straight ahead. I had never thought about it but that is the way you skate although 45 degrees seems kind of extreme. If you look ...
January 2, 2016

Hmm, I can not help
... but if you do get help, let me know. We have three dogs that desperately need training. Luckily they are tiny.
January 2, 2016

clickable link I hope
http://en.wikipedia.org/wiki/Pacific_Route
January 2, 2016

Social Studies (Check, Please!)
I might go a bit further and claim that Russia would have collapsed without the convoys to Murmansk and to their Pacific seaport Vladivostok. https://en.wikipedia.org/wiki/Pacific_Route
January 2, 2016

Math
c * 11.5 + p * 13 = 1255 c + p = 100
January 2, 2016

math
You are welcome.
January 2, 2016

math
For example: Boole was appointed to the chair of mathematics at Queens College, Cork in 1849. In fact he made an application for a chair in any of the new Queen's Colleges of Ireland in 1846 and in September of that year De Morgan, Kelland, Cayley, and Thomson were among ...
January 2, 2016

math
http://www-history.mcs.st-andrews.ac.uk/Biographies/Boole.html
January 2, 2016

Math
No problem. You are welcome.
January 2, 2016

Math
Angle at C is common to triangles ACD and to ACB since angles in both triangles add to 180, angle ADC = twice angle ABD call angle CAD = T then BAD = T call angle ABD = A then angle ADC = 2A then sin T / 6 = sin 2A /x sin 2T / 11 = sin A /x sin T / 5 = sin (180-2A)/8 = sin 2A...
January 2, 2016

Physics
I did this a few days ago. http://www.jiskha.com/display.cgi?id=1451329598
January 2, 2016

maths
3/4*1/3 = 1/4
January 2, 2016

Calculus help plz
Thanks for figuring out what was meant. I just threw up my hands in frustration.
January 2, 2016

Calculus
Happy to help :)
January 2, 2016

Calculus Huh??
Is this supposed to be: ∫((cos^3(x)/(1-sin^2(x)) dx ?? 1 - sin^2 x = cos^2 x because cos^2 x + sin^2 x = 1 so you have ∫ cos(x) dx the derivative of the integral is what you already have, cos x the integral is sin x + c
January 2, 2016

Physics
m g = 2890 m g - 2200 = m (.36) You did not say what your question is but you can solve that for m and for the local g
January 2, 2016

Math
depends what you mean by intense. If amplitude is 27 times log A = 3.2 so A =1584 B = 1584 * 27 = 42792 log B = 4.63
January 1, 2016

mechanics
You are asking me to write a chapter in your text book. Any physics text can help you better than I can. for the first question: F = G Me m/r^2 = (GMe/r^2) m for changes in r that are small compared to earth radius, like from here to the top of Mt Everest this quantity is ...
January 1, 2016

physics
40 cycles / (8*60 seconds) = .083 Hz
January 1, 2016

Physics
How long to fall 46-1.8 = 44.2 meters ? 44.2 = (1/2) g t^2 t = sqrt (88.4/9.81) t = 3 seconds d = u t = 1.20 * 3 = 3.6 meters
January 1, 2016

Reposting calculus help plz
y dy = x dx + x^3 dx y^2/2 = x^2/2 + x^4/4 + c
January 1, 2016

mechanics
torque = moment of inertia * angular acceleration 40 * 0.20 = 30 alpha alpha = .267 radians/sec^2 omega = alpha * t omega= .267 * 4 = 1.07 radians/sec angle = (1/2) alpha *t^2 = .5 *.267 *16 = 2.136 radians divide by 2 pi = .34 revolutions torque * angle = work in = 8 * 8.53...
January 1, 2016

Maths
assume you mean 24 m not cm distance d from tree tan 45 = (24-h)/d tan 60 = h/d so (24-h)/tan 45 = h/tan 60
January 1, 2016

Maths/physics need help agn
up force from each student = 81 N = F cos 60 = F/2 so 162 N
January 1, 2016

Maths/physics
(1/2) m v^2 = (1/2) k x^2 .5 (1600) = .5 k (.04) k = 40,000 Newtons/meter F = k x = 40,000 (.2) = 8000 N
January 1, 2016

maths
area of brick = .25*.12 = .03 m^2 area of yard = 20*30 = 600 m^2 number of bricks = 600/.03 = 20,000
January 1, 2016

Math parentheses ?
do you mean 3 - x = sqrt (x^2 - 5) ?? if so 9 - 6 x + x^2 = x^2 - 5 6 x = 14 x = 7/3 = 2.33 x^2 - 5 must be + so |x| >/= sqrt 5 or 2.24
January 1, 2016

Calculus
hanging mass = 100 + 2 x F = g(100+2x) do dW = F dx from x = 0 to x = 20 W = g (100 x + x^2) at 20 - at 0 = g (2000 + 400) = g (2400) = 23520 Joules then from x = 0 to x = 10 g (1000 + 100) = 1100 g = 10780 Joules subtract I get 12740 Joules
December 31, 2015

Electric field
(1/2) m v^2 = q V m is electron mass q is electron charge (assume positive)
December 31, 2015

Trig
CSC (5PI/6) ?? 6pi/6 or pi is 180 degrees, the - x axis so we are pi/6 or 30 degrees above the - y axis the sin of that angle (150 deg) is 1/2 so the answer is 1/(1/2) or 2
December 31, 2015

physics
Torque = I alpha 5.2 * .8 = 1.4 alpha alpha = 2.97 radians/second^2
December 31, 2015

physics
The current now has three choices for where to go, but the voltage is the same for all three. itotal = V/R + V/r + V/R itotal = 3 V/R = V/(R/3) which is the voltage divided by the equivalent resistance, R/3
December 31, 2015

Science
The type of force is therefore electrostatic (Coulomb) force in the simple model of atoms.
December 31, 2015

Science
I am no chemist but those are all compounds between Hydrogen and halogens which desperately want to grab an electron to fill their outer shells so I would expect Hydrogen bonds where the Hydrogen partially gives up its sole electron.
December 31, 2015

Electric field
1 electron volt or 1.6*10^-19 Joule
December 31, 2015

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