Saturday
April 25, 2015

Posts by STEVE


Total # Posts: 30,783

trigonometry
v = 2π*14in/rev * (.5/2π)rev/s = 28 in/s .5rad/s * 1rev/2πrad * 60s/min = 4.77 rev/min .5rad/s * 180°/πrad = 90/π °/s
April 8, 2015

maths
this is just an A.P. with d = 4 a = 100-20*4 = 20 So, the sum of 21 rows is S = 21/2 (20+100)
April 8, 2015

math
draw your triangle the other side is √15 since we are in QII and sin is positive, x = -√15 y = 1 r = 4 so, cosx = -√15/4 Now use those values to plug into your half-angle formulas.
April 8, 2015

Pre-calc
Or, you can go the other way sin(7x) = sin(6x)cos(x) + cos(6x)sin(x) and start expanding those as well, till all you have left is a bunch of sin(kx).
April 7, 2015

Pre-calc
http://www.wolframalpha.com/input/?i=%28sinx%29%5E7 will show the answer you need. sin^7 = sin(1-cos^2)^3 Now you can start expanding and using the sum formulas. I'm sure a google search will show up all the gory details.
April 7, 2015

math
why use } when / is available? (4/9)(1/8) = 1/18 (1/18)(1/3) = 1/54
April 7, 2015

Math
correct.
April 7, 2015

Math
There is clearly a typo in the above, since the function is a parabola which opens upward, and so has no maximum. If we go with y = -6x^2+42x-60 then that works out to y = -6(x^2-7x+10) = -6(x-5)(x-2) The vertex is at x = 3.5, so that means 3500 boards. You know, if you keep ...
April 7, 2015

Math
-5x^2 - 30.5x = -1/10 (50x^2 - 305x) = -5/10 x (10x-61) I suspect a typo, since the roots of the above are clearly 0 and 6.1
April 7, 2015

Math
no, it can be any real number.
April 7, 2015

Calculus
see the related questions below.
April 7, 2015

math
I'd think so, since the eye perceives the linear dimensions, which grow much more slowly than the volumes.
April 7, 2015

I NEED HELP WITH THIS
how far do you get? Do you not have any ideas? If not, you'd better review the textbook where it discusses this. To start, A series: R = r+r+r parallel: 1/R = 1/r + 1/r + 1/r
April 7, 2015

grammar
I agree with (a) I think if it had said each delegate and each alternate, then (b) would be better.
April 7, 2015

math
you ought to explain what "1 } 10" means.
April 7, 2015

math
P is the same as if there were a 5-section wheel with just the numbers 1-5.
April 7, 2015

Math
you mean you can figure out 2*3+5, but you cannot do the same for 1,2,4? Ai caramba!
April 7, 2015

Algebra
A: LW = √18√24 = √(18*24) = √(2*3^2 * 2^3*3) = √(2^4 3^3) = 12√3 since A = LW, what if you have (L/2)(W/2)?
April 7, 2015

geometry
without some kind of explanation of the angles and the diagram, I don't think you can get much help here. By the way, ≅ is congruent. Rather than describing the symbol, why not just say congruent? And your opening sentence is bogus, since you don't say what <1...
April 7, 2015

math help
F is undefined where the denominator is zero #2 ? #3 domain is all reals except for the undefined value(s) #4 y-intercept (at x=0): -6/(0-3) -1 = -6/-3 - 1 = 2-1 = 1 x-intercept (at y=0) -6/(x-3)-1 = 0 -6 - (x-3) = 0 -6-x+3 = 0 x = -3
April 7, 2015

Math
well, 12^2 = 144, so you want 6x+6 = 12 or 6x+6 = -12
April 7, 2015

Math
#1 √(x+4)-3 >= 4 √(x+4) >= 7 x+4 >= 49 x >= 53 #2 t = √(d/16), so we want (using t in seconds) √(d/16) > 60 d/16 > 3600 d > 57600
April 7, 2015

Math
(2w+a)^8 = ... + 16wa^7 + ... (-x+b)^7 = ... - 35x^3b^4 (y-2z)^4 = ... + 24y^2z^2 So, I get -13440wx^3y^2z^2
April 7, 2015

science.......
(a) 60W * 1 hr = 60 Wh (b) .060 kWh * .1745 $/kWh = 0.01 200kJ/270s = 740W
April 7, 2015

math
well, how many points in the empty set?
April 7, 2015

UNISA
to accrue to how much?
April 7, 2015

math
If I interpreted the rather garbled English, you want x and y where x+y = 44 xy = 1280
April 7, 2015

math
eliminate z and you have 100-x-y = 200-10x-2y 9x+y = 100 So, you could let x=10, y=10, that would make z=80 Or, you could have x=1,y=91, so z=8 There is no unique solution.
April 7, 2015

algebra
I think you need some parentheses in that horrid run-on expression. As written it could mean x^2 - 9y^2/xy / 1/y - 3/x = x^2 - 9y/x * y/1 - 3/x = x^2 - 9y^2/x - 3/x = x^2 - 3(3y^2+1)/x There are, of course, many other ways to parse all that stuffed jammed together. Unless ...
April 7, 2015

science 1 question
ahem. it does not form energy by spinning. It changes electrical energy into kinetic energy (of motion).
April 6, 2015

science 1 question
do you feel sucked into the fan when you turn it on? Does it feel like when an elevator starts? That's gravitational. Hint: what the heck does a fan do when you turn it on?
April 6, 2015

Math
well, ya got a table? Maybe these graphs will help you out in determining the transformations required. http://www.wolframalpha.com/input/?i=plot+y%3D3%5Ex%2C+y%3D3%5E%28%E2%88%92%28x%2B1%29%29+%E2%88%922
April 6, 2015

Calculus
Just curious. How do you get from 2(2)dy/dt+(2)(-1)(-4)+6(-1)^2=0 to 10 dy/dt+8=0 ???
April 6, 2015

Calculus
Assuming you mean c^2 = x^2 + 98√(x+57) then c^2(4) = 4^2 + 98√61 = 16+98√61 c(4) = 27.95 2c dc/dx = 2x + 49/√(x+57) at x=4, we have 55.90 dc/dx = 8+49/√61 dc/dx = 0.255 Of course, I might have misread the function, with all those pesky words ...
April 6, 2015

Chemistry
(a) you are diluting the concentration by a factor of 6/.25=24 So, you will need 20/24 ml of 6M solution to produce 20ml of .25M solution. The rest, of course, is water. Do the others in like wise.
April 6, 2015

Calculus
Hmm. Ignore my previous comment. Still, if the functions are as given, Reiny's answer appears correct. Are there mis-types somewhere?
April 6, 2015

Calculus
well, what is P? That is the rate you are calculating.
April 6, 2015

1 question omh help??
Looks like C to me.
April 6, 2015

intermediate algebra
Hmm. I get (3(x-3) - x(x+3) + 1(x-3)(x-3)) / ((x-3)(x-3)(x+3))
April 6, 2015

Physics
momentum must be conserved: 1*3 + 2*0 = (1+2)v Although, I fail to see how they could properly roll, if sticking together after such a collision.
April 6, 2015

Physics
assuming the original mass was really 20.0 kg, total momentum must remain at zero, so 15.0*2 + 5.0v = 0
April 6, 2015

Pre-Calculus
not quite. since (x+a)^2 = x^2+2ax+a^2, x^2+9x = x^2+9x+(9/2)^2-(9/2)^2 x^2+9x+20 = (x + 9/2)^2 + 20-81/4 = (x + 9/2)^2 + 319/4
April 6, 2015

calc
f = 2x+15-19e^x f' = 2-19e^x f'(0) = 2-19 = -17 so, the tangent line is y+4 = -17(x-0) see the graphs at http://www.wolframalpha.com/input/?i=plot+y%3D2x%2B15-19e%5Ex%2C+y%3D-17x-4
April 6, 2015

calc
x = e^(8-p) revenue is x*p = pe^(8-p) profit = revenue-cost = xp-x = x(p-1) = (p-1)e^(8-p) so, if y is the profit at price p, dy/dp = (2-p)e^(8-p) set the price at p=2
April 6, 2015

chemistry
if you mean g/L, that would be 1mole/22.4L = 0.759 g/L
April 6, 2015

Calculus
well, geez, just plug in e^2 into f'(x) f'(e^2) = 4(ln(e^2))^3/e^2 = 4(2)^3/e^2 = 32/e^2 remember ln(e^u) = u e^(ln u) = u
April 6, 2015

algebra
what is that 4 doing there? is 4√y supposed to mean 4th root of y? x^(11/10) is 10th-root(x^11)
April 6, 2015

math
man, look up your point-slope formula: y-5 = 2/3 (x+1)
April 6, 2015

geometry
transitive: A≅B and B≅C ==> A≅C No idea what the diagram shows.
April 6, 2015

geometry
M=(A+B)/2 clearly AM=MB = 1/2 AB Look up your distance formula to figure length of AB.
April 6, 2015

Calculus 2 (Series)
see the solution here: http://www.math.ucla.edu/~hendricks/CalculusIISummer2011/calc2practicefinalsolutions.pdf
April 6, 2015

math
5f+4s = 14.80 (3/4)f = (3/5)s s = 1.85
April 6, 2015

maths
before: TTT after: TTT TTT so, how many T's?
April 6, 2015

Differential Equation 4
no ideas on these problems? Homework dumps are discouraged.
April 6, 2015

Differential Equation 3
why the stupid carets? These are not exponents. (x^2+1)y"+2xy'=0 Since y = c1 + c2 arctan(x) I suspect you can now come up with the series.
April 6, 2015

algebra
that copy/paste stuff will kill ya every time!
April 6, 2015

calculus
v(t) = ds/dt = 128-32t So, plug in t=4.
April 6, 2015

math
for m months, the cost c is c = 127 + 28m now plug in m=9 for the cost of 9 months. actually, c is the cost of joining and then using the club. The question is poorly worded.
April 6, 2015

Precal
so, if u=3^x, you have u^2 - 4u + 3 = 0 You can handle that, I presume?
April 6, 2015

calculus
wrong h = 130 + 35t - 16t^2
April 6, 2015

ET 1210 FUNDAMENTALS
E/R -> (2E)/R = 2E/R
April 6, 2015

ET1210 DC/AC FUNDAMENTALS
I=E/R so, the new I will be E/(R/2) = 2E/R
April 6, 2015

math
since the speed is the same, 7/60 = x/24
April 6, 2015

Physics
well, what was the date 250 years ago? A light-year is the distance light travels in a year. So, it took the light 250 years to get to earth.
April 6, 2015

Precal
Dan and Reiny just did one of these for you. Just make sure everything is expressed as powers of 3, then equate the powers to solve for x.
April 5, 2015

physics
momentum is mv surely you can figure the starting and ending values. The time taken makes no difference.
April 5, 2015

math
the slope is the constant of variation. In this case, 11. This is just a special case of the slope-intercept form y = mx+b where b=0.
April 5, 2015

PHYSICS
work = force * distance so, how far does it travel in 1 second? F=ma, so a=F/m s = 1/2 at^2 = 1/2 (F/m) t^2
April 5, 2015

Precal
Since 25 > 21, the ellipse is long on the y-axis. So, the vertices are (0,5) and (0,-5) You should have immediately seen your answers were incompatible. The foci must lie on the major axis. Your foci are correct.
April 5, 2015

Math
12000(1+.08/4)^(4*4) = 16473.43 900*(1.02^16+1.02^15+...+1.02^1) = 900(1.02^16 - 1)/(1.02-1) = 16775.36 Have I missed something? My answers are about 1/2 the expected values.
April 5, 2015

AP CALC
#1. solve for t in 0.985^t = 0.8 #2 dy/dx = 3√x √y dy/√y = 3√x dx 2√y = 2x^(3/2) + c at (1,4) we have 2√4 = 2*1^(3/2)+c 4 = 2+c c = 2 2√y = 2x^(3/2)+2 at x=0, 2√y = 2 y = 1 check: y = (x^(3/2)+1)^2 y' = 2(x^(3/2)+1)(3/2 &#...
April 5, 2015

trig
since sin^2 + cos^2 = 1, cos(23) = √(1-p^2) cos(113) = cos(23+90) = cos(23)cos(90) - sin(23)sin(90) = -p sin(46) = 2sin(23)cos(23) = 2p√(1-p^2) Time to review your basic sum/double-angle formulas
April 5, 2015

maths
sin(2x) = 1/2 tan(x) 2sinx cosx = 1/2 sinx/cosx 4sinx cosx = sinx/cosx Clearly, sinx=0 is one intersection Elsewhere, we can divide through by sinx, and we have 4cos^2x = 1 cosx = ±1/2 Now you can easily find the points you want.
April 5, 2015

Math
what? You can't take a number, multiply it by -2 and subtract 4? y(0) = -2*0-4 = -4 Clearly, only C and D are possible answers. Now find y(1) the same way and you should get the correct choice.
April 5, 2015

algebra
If the sons are age a and b, with a<b, f+a+b = 50 f-4 = 8(b-4) f+4 = 4(a+4)
April 5, 2015

Geometry help
if the perimeter is p and the apothem is a, then the area is 1/2 ap #1. correct: 12/√2 #2. hint: the triangle's altitude is 18. #3. side is 12
April 4, 2015

Differential Equation 1
well, the solution of the homogeneous equations is y = c1 cos(2lnx) + c2 sin(2lnx) + c3/x^2 Not sure what to do with the t's, though.
April 4, 2015

Physical Science
(12/120) * 500
April 4, 2015

Physics
I think you might get a clearer picture of the situation by reading the discussion here: http://hyperphysics.phy-astr.gsu.edu/hbase/mechanics/earthole.html
April 4, 2015

math - incomplete
42
April 4, 2015

Consumer Math
correct
April 3, 2015

Algebra 2
pick any value for x, say 20 Then 2*20+y = 8 40+y = 8 y = -32 So, (20,-32) is one pair Or, pick any value for y, say 0 Then 2x+0=8 x=4 So, (4,0) is another pair
April 3, 2015

Math
if the circumference is 1/40 as big, then so is the diameter.
April 3, 2015

Physics
If the amplitude is A, then it goes from -A to +A, or a distance of 2A. But during one period, it goes up and back again, for a distance of 4A.
April 3, 2015

geometry
or, you can use a compound inequality. 34-22 < x < 34+22 12 < x < 56
April 3, 2015

Geometry
correct
April 3, 2015

Geometry
A pilot sees a guy at an angle of depression of 50 degrees. If the pilot is 200 degrees from the guy, how high is the pilot? Would it be sin(50) x 200?
April 3, 2015

pre calculus
oops (b) [100*20 + x(20-5)]/(100+x)
April 3, 2015

pre calculus
(a) ?? unless the pricing varies somehow the cost for x skiers will always be the same (b) [100*20 + x(20-5)]/x ...
April 3, 2015

PHYSICS
If the parts are x and M-x, then F = Gx(M-x)/r^2 = G/r^2 (Mx-x^2) This is just a parabola, with vertex at M/2. That is, the force is maximum when the masses are equal. It's like the area of a rectangle with constant perimeter is greatest if it is a square.
April 3, 2015

Math
if x sell at $40, then the rest (6000-x) are $26, so 40x + 26(6000-x) = 190500
April 3, 2015

Geometry
the slope of AB is -5/3 so, which if the choices has that same slope?
April 3, 2015

math
try using a common denominator again. Then pick the smallest one.
April 3, 2015

m ath
2^-2 = 1/2^2 = 1/4
April 3, 2015

math
rewrite them all with denominator of 8: 4/8 5/8 7/8 6/6 now just sort them by numerator.
April 3, 2015

Calculus
if xi is the right endpoint, then 3 cannot be x1. That leaves only c and d for choices. Since the interval length is 2, and the number of divisions is 4, each interval is .5 in width. Looks like (c) to me. BTW, (d) is the set of midpoints.
April 3, 2015

Math
thank you
April 3, 2015

Math
If I know all 3 angles of a right triangle and the hypotenuse how do I figure out the short side length of the triangle?
April 3, 2015

6th Grade Math ASAP!!!
you're right -- it is complex. Especially so since you don't seem to have any questions about it.
April 3, 2015

Math
rotation through 180° changes both signs. So, (3,-5) -> (-3,5) Did you actually plot your solution? You would see that it was nowhere near the rotated point. an equilateral triangle has axial and rotational symmetry.
April 3, 2015

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