Wednesday

January 18, 2017
Total # Posts: 28,788

**Calculus AB**

5, 12, 13 right triangle here so sec = 1/cos = 13/5 then 3, 4 , 5 tan = 1/cot = 4/3 so sin = 4/5 so 13/5 - 4/5 = 9/5

*July 30, 2016*

**Calculus AB**

h = ln (sin x) look at this at x = 0, x = pi/2, x = pi/4, x = 3 pi/4 , x = pi , note sin x must be >0 so only quadrants 1 and 2 ln sin 0 undefined ! ln sin pi/4 = -.346 ln sin pi/2 = 0 ln sin 3 pi/4 = -.346 etc :)

*July 30, 2016*

**Calculus AB**

y = a cos (k x - b) + c a and c are easy because c is average of 8 and -2 or 3 and a is thus 5 y = 5 cos (k x - b) + 3 cos is max of 1 at k x - b = 0 k*3-b = 0 so b = 3 k so y = 5 cos (k x - 3 k) + 3 cos is min of -1 at k x - b = pi kx - 3k = pi but x = 7 here so 7 k - 3 k = ...

*July 30, 2016*

**English**

a piece of ONE banana well, again ONE banana or just the singular type of fruit again not two apples but two pieces of apple

*July 30, 2016*

**Math**

if 4 t = 2 pi t = pi/2 if 6 t = 2 pi t = pi/3 so we need at least t = 0 to t = pi/2 or any other interval of length pi/2

*July 30, 2016*

**Math typo**

t = -1 + 5 t ? I doubt it then 1 = 4 t and t = 1/4 x = 2 - 3 (1/4) period

*July 30, 2016*

**Physics**

average force = change of momentum/time

*July 30, 2016*

**Physics**

NEWTON'S FIRST LAW !!!! 75 * 5 = (75+40) * v

*July 30, 2016*

**Physics**

mu static = friction force/normal force = 300/400 similarly mu dynamic = 200/400 Why are you asking questions that I am sure are covered in your text?

*July 30, 2016*

**maths**

ten sides? going around the outside we have to turn right ten times that means each time we turn right 36 degrees which is 360/10 that means the interior angle= 180 - 36 = 144 degrees in radians this is pi - 2pi/10 = 5 pi/5 - pi/5 = 4 pi/5

*July 30, 2016*

**statistics**

We need the sum of probabilities of 6, 7 and 8 This is much more advanced than your previous questions and requires use of the binomial distribution rules. P(x=k) = C(n,k) p^k p^(n-k) where C(n,k)=n!/[k!(n-k)!] so for example the P(x=6) is P(x=6)= C(8,6) .33^6 * .67^2 where C(...

*July 30, 2016*

**math**

b is bigger than a and smaller than c

*July 29, 2016*

**statics is not statistics**

....and statistics is not statics * | 1 2 3 4 5 6 _______________ 1 | 2 3 4 5 2 | 3 4 5 3 | 4 5 4 | 5 5 | 6 | so 10/36

*July 29, 2016*

**statics**

.....and you mean statistics :)

*July 29, 2016*

**statics**

I did NOT say 28 I said 28 divided by the sum

*July 29, 2016*

**statics**

You mean statistics by the way. I replied because I do statics and dynamics. It is just luck I knew the probability question answer.

*July 29, 2016*

**statics**

sum = 33 + 34 + 30 + 28 answer = 28 / sum

*July 29, 2016*

**statistic**

recipe is here: http://davidmlane.com/hyperstat/z_table.html

*July 29, 2016*

**physics**

d = .05 meter Fx = k [Q^2/.05^2]cos 30 from each Fy cancels so it is just 2Fx (repels of course because same sign)

*July 29, 2016*

**general solution**

Call the time, which I think is a typo, T distance is d t1 = time out t2 = time back t1 + t2 = T t1 = d/55 t2 = d/330 so d/55 + d/330 = T d = T /(1/55 + 1/330)

*July 29, 2016*

**too long a time**

7 seconds?

*July 29, 2016*

**math**

Trick question (1/cos A)(cos A) = 1 unless cos A = 0 but what is cos 90 ? If A = 90. in fact the secant is just plain not defined. http://socratic.org/questions/what-is-the-exact-value-of-sec-90

*July 29, 2016*

**probability**

Consider these events independent because there are a lot more than 4 children in Ghana. Use binomial distribution. C(4,4)(.65)^4 (.35)^0 1 * .65^4 * 1 .65^4 note C(n,k) = n!/[k!(n-k)!] defined as 1 for k = 0 see http://www.mathsisfun.com/data/binomial-distribution.html

*July 29, 2016*

**Stats**

http://www.google.com/search?q=david+m+lane+normal+curve&ie=utf-8&oe=utf-8

*July 29, 2016*

**Chemistry**

C2D3 has a solubility product constant of 9.14×10−9. What is the molar solubility of C2D3? Express your answer with the appropriate units.

*July 28, 2016*

**Math**

92 + 64 - (73+89) - (66-49) etc down to -42-(-81)-(-73)=? = -42 + 81 + 73

*July 28, 2016*

**makes no sense**

how much time? how many km, whatever?

*July 28, 2016*

**math**

One faucet fills 100 gal in 18 min so a faucet does (50/9) gal/min 6 *(50/9) t = 25 6*(2/9)t = 1 t = 9/12 = 3/4 minute

*July 28, 2016*

**math**

2016 - 2000 = 16 16 * 7 = 112 224 - 112 = 112 half the original

*July 28, 2016*

**mathematics**

x(g+b) have not finished .65 g have not finished .55 b have not finished .65 g + .55 b = x(g+b) but g = 3 b so .65(3 b)+.55 b = x ( 4 b ) (1.95+.55)b = 4 x b x = 2.5/4 = .625 so 62.5 %

*July 28, 2016*

**world history**

First of all, who says? Although the habit is to treat Chinese dynasties as succeeding, there is no reason they should not have overlapped. That said, they had, as the Chinese always had, nomadic tribes to the north and west and the bleak ocean to the east. Mostly mountains ...

*July 27, 2016*

**science(physics)**

momentum = 0.100 * 20 = 2 kg m/s distance into plank = .020 meter average speed in plank = 20/2 = 10 m/s time in plank = .020/10 = .002 s average force = change in momentum/time = 2/.002 = 1000 Newtons

*July 27, 2016*

**math**

(9/36)*900 = 900/4 = 225

*July 26, 2016*

**Math**

This is not a submarine but a research submersible. Submarines do not go much deeper than a couple of boat lengths. 8 * 60 + 37 = 517 seconds 517 seconds * 25 ft/s = 12,925 feet Although that is far deeper than a submarine dives, it is less than half as deep as the Mariana ...

*July 26, 2016*

**Chemistry**

How much H3PO4 is needed to neutralize 1 liter of a 0.75M solution of NaOH? (in moles)

*July 26, 2016*

**Math**

8 sin 30 + 8 sin 120 8 (1/2) + 8 (1/2) sqrt 3

*July 26, 2016*

**math**

must be combined age? p = 2 j p-17 + j-17 = 33 p + j = 67 2 j + j = 67 3 j = 67 j = 67/3 = 22 1/3 so p = 134/3 = 44 2/3

*July 26, 2016*

**physics**

h = Hi + Vi t - 4.9 t^2 v = Vi - 9.81 t when is v = 0 ? (the top) t = 30/9.81 = 3.06 seconds coasting up to a stop so h = 50 + 30 (3.06) - 4.9 (3.06)^2

*July 26, 2016*

**Physics**

You kidding? 200 - 3(45)

*July 26, 2016*

**physics**

v = Vi - 9.81 t h = Hi + Vi t - 4.9 t^2 42 = 0 + Vi(2) - 4.9(4) Vi = 30.8 meters/ second when it hits ground, v = -30.8 m/s v = Vi - 9.81 t -30.8 = 30.8 - 9.81 t t = 6.28 seconds

*July 25, 2016*

**Chemistry**

Thank you so much!

*July 25, 2016*

**Chemistry**

What volume of nitrogen dioxide (in L) is produced from the complete reaction of 16.87 of lead (ii) nitrate at STP

*July 25, 2016*

**college physics**

time for one wave = period = 1/f = 10/30 so f = 3 Hz

*July 25, 2016*

**physics**

u = 10 m/s forever v = -gt = -9.81 (3) = - 29.4 m/s check if it hit the ground d = (1/2) g t^2 = 4.9 * 9 = 44.1 so still in the air speed = sqrt (10^2 + 29.4^2)

*July 25, 2016*

**Maths**

a + 20 = 3 (180-a) a + 20 = 540 - 3 a 4 a = 520 a = 130 180-a = 50

*July 25, 2016*

**Maths**

(n + m)/2 = 15 so n + m = 30 m = (30-n) (n m )^.5= 9 n m = 81 n(30-n) = 81 -n^2 + 30 n = 81 n^2 -30 + 81 = 0 (n-3)(n-27) = 0 3 and 27

*July 25, 2016*

**General Mathematics**

http://www.jiskha.com/display.cgi?id=1469428320

*July 25, 2016*

**Maths**

7 +8 +3 = 18 so 2 are white 2/20 = 0.1

*July 25, 2016*

**huh? typos?**

maybe 2 meters deep and find volume not height? if so v = w L d = 20 *100 *2 = 4,000 m^3

*July 25, 2016*

**Math (Rational Inequality)**

x^2 h = 8 x = sqrt(8/h) if h = x x = h = 2 if x > h, not allowed if x < h then h > 2 so x < 2

*July 25, 2016*

**algebra**

Well, you know 48 = 16*3 You know that 3/3 = 1 so multiply 3/16 by 3/3 and get 9/48

*July 25, 2016*

**ststistics**

binomial distribution p = .24 1-p = .76 n = 10 P(2) = C(10,2).24^2 (.76^8) but C(10,2) = 45 so 45 * .0576 * .111 = .288 P(1) = 10 * .24 * .76^9 = .203 so answer to b is 1 - .288 - .203 c is same way but boring. you do it

*July 25, 2016*

**Hey wait a minute**

This is very, very similar to one I already helped you with. Please try them yourself. It does not do you any good to have us do all the problems for you. The idea is that we can help, but not do virtually the same problem over and over for you. http://www.jiskha.com/display....

*July 24, 2016*

**MATH**

let x = tan t then dx = sec^2 t dt sec^2 t dt/[ tan t (1+tan^2 t) ] NOTE: 1+tan^2 t = sec^2 t !!! wow that helps :) so we have dt/tan t = ctn t dt = ln (sin u)

*July 24, 2016*

**Math**

u = 1 - y^2 du = -2 y dy or dy = du/-2y ((y^3)/(u^2))[du/-2y] (-1/2)y^2 du/u^2 but y^2 = 1-u so -(1/2)(1-u) du/u^2 = (u/2)du/u^2 - (1/2)du/u^2 = (1/2) du/u - .5 u^-2 du finish and check my arithmetic :)

*July 24, 2016*

**Someone Please Help me- PreCalc**

x^2 + y^2 = 1 16/49 + y^2 = 49/49 y^2 = 33/49 y = +/- sqrt (33) /7 so since in Q IV where y is negative (4/7, -sqrt(33)/7 )

*July 24, 2016*

**physics**

10 * 100

*July 24, 2016*

**physics**

potential energy at top = kinetic energy at bottom m g h = (1/2) m v^2

*July 24, 2016*

**maths**

24 + 5 - 17

*July 24, 2016*

**Physics**

Oh, do cos wt = -1/2 as well

*July 24, 2016*

**Physics**

x = X sin w t v = X w cos w t so X w cos w t = (1/2) X w cos w t = 1/2 w t = 60 degrees, 300 degrees etc or in radians pi/3 etc so what is x/X when wt = pi/3 etc x/X = sin wt x/X = sin 60, 300 etc x/X = .866 , -.866 etc

*July 24, 2016*

**Math**

x + 24 = 36 ?? -24 = -24 ---------------add x + 0 = 12 so x = 12

*July 23, 2016*

**Math**

.3(10) = 3 .3(10+10) = 3+3 = 6 .3(10+10+10) = 3+3+3= 9

*July 23, 2016*

**physic**

kinetic energy = (1/2) m v^2 that goes into heating the brakes (use Joules not calories) energy =specific heat*mass*(Tend-Tbegin)

*July 23, 2016*

**Science**

(1/2) m v^2 = (1/2)(1/2)(9) = 9/4 Joules

*July 22, 2016*

**math**

first blue: 6/16 second blue 5/15 so 3/8 * 1/3 = 1/8 = 0.125

*July 22, 2016*

**math whoops 4/13**

sorry, 4/13

*July 22, 2016*

**math**

careful !

*July 22, 2016*

**math 11/36**

http://davidmlane.com/hyperstat/A136602.html

*July 22, 2016*

**math**

Yes,note unlike the other two questions because red and spade are mutually exclusive

*July 22, 2016*

**physicis**

metal A length x metal B length (15-x) x(4.3)(pi r^2) + (15-x)(6.3)(pi r^2) = 21757 4.3 x + 94.3 - 6.3 x = 21757/(81 pi) 2 x = 8.8 x = 4.4 cm

*July 22, 2016*

**Physics**

m = 670/g = 670/9.81 = 68.3 kg F = G m Ms/(r^2) F=6.67*10^-11*68.3*1.99*10^30/7500^2

*July 22, 2016*

**stats**

http://davidmlane.com/hyperstat/z_table.html

*July 22, 2016*

**PHYSICS**

well, I am just going to estimate iron density about 8 times water 8000 kg/m^3 or 8 g/cm^3 8 L pi r^2 = 8(85)(3)(2.5)^2 about 8 * 85 *3 * 6.3 or 12852 grams 12.8 kg no problem :) less than 30 pounds

*July 22, 2016*

**maths**

n cupcskes n/6 to neighbor , 5n/6 remain (7/10)(5n/6) to sister or 7n/12 to sister (3/10)(5n/6) remain or n/4 remain so n/4 =12 n =48

*July 22, 2016*

**Physics**

How high does it go? v = Vi -9.81 t at top v = 0 0 = 14 -9.81 t so t = 14/9.81 then h = 100 + 14 t - 4.9 t^2 now fall from h v^2 = 2 g h

*July 22, 2016*

**Algebra**

x and (60-x) 2 x -.5(60-x) = 10 2 x -30 +.5 x = 10 2.5 x = 40 25 x =400 x = 16 60-x = 44

*July 22, 2016*

**Algebra**

(y-a)^2 = y^2 - 7 y + p y^2 - 2 a + a^2 = y^2 - 7 y + p 2 a = 7 a = 7/2 so p = a^2 = 49/4

*July 22, 2016*

**Physics,Mthe**

mass/volume = density =100/10 = 10 but you have given no units so it could be anything at all.

*July 22, 2016*

**Physics**

I am not going to just give you the answers to these very basic questions. Try yourself and maybe someone will help if you get messed up.

*July 21, 2016*

**No way !**

No, I refuse to just answer. You say and tell us why. What do you think? What is the difference between mass and weight? Would it be different at different locations in the body?

*July 21, 2016*

**American History**

Budgets cuts in our Defense has led to inefficient weapons available to the soldiers to fight wars here in America or Overseas. ??????????????????? Please compare US defense budgets and resulting weaponry to those of other countries.

*July 21, 2016*

**Math**

For what value(s) of r is r^2+5r+6/r+2 equal to 0? A) -2 only B) -3 only C) 3 only D)-2 or -3 E) 2 or 3 I got A but it is incorrect and I'm still confused Thanks

*July 20, 2016*

**Chemistry**

How many grams of hydrogen peroxide (H2O2) must be added to 1,500 ml of water to produce a concentration of 1.33 m (molal solution)?

*July 20, 2016*

**Math**

checks at http://www.mortgagecalculator.org/

*July 20, 2016*

**Math**

payment = principal [ r/ (1 - {1+r}^-n) ] here principal = 200,000 r = .10/12 = .0083333333..... n = 25*12 = 300 = 200,000 [ .00833... / (1-{1.00833..}^-300) ] = 200,000 [ .009087 ] = 1817.40

*July 20, 2016*

**math**

7 * 9 = 63 315/63 = 5 so 7 * 9 * 5 = 315

*July 20, 2016*

**Geometry**

y = 2 x - 5 to y = 2 x moves up 5

*July 20, 2016*

**Math**

have played x have won .75 x will have won .75 x + 4 will have played x + 4 so .75 x + 4 = .80 (x +4) 4 - .8*4 = .05 x 4 - 3.2 = .05 x .8 = .05 x 800 = 5 x x = 160

*July 20, 2016*

**Algebra**

c^2 + 18 c - 175 = 0 (c + 25)(c - 7) = 0 c = 7 or c = -25

*July 20, 2016*

**statistics**

15951/13 = 1227 per yesr

*July 20, 2016*

**Math**

7 1/2 = 15/2 15/2 / 3/4 = 30/3 = 10 =============== or 10 * 3/4 = 30/4 = 7 1/2

*July 20, 2016*

**algebra**

Well, if the denominator is constant and x is alone up there (no x^2 or sin x or anything) then yes

*July 19, 2016*

**Northwest is not 30 deg n of e**

when you get the geometry figured out look at: http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/forwir2.html

*July 19, 2016*

**Nobody knows**

we do not know what the dimensions were on the plans, or alternately the area. If you know the area on the plan, A in^2 then Areal = A (9 ft^2/6.25 in^2)

*July 19, 2016*

**physics**

Well, you could use Maxwell's equations, but it might be easier to make a common sense guess. If moving the magnet makes a voltage, then it is likely that moving it faster will make a bigger voltage.

*July 19, 2016*

**Physics**

ps: That is what potential is all about.

*July 19, 2016*