Tuesday

September 27, 2016
Total # Posts: 44,101

**Maths**

drop an altitude from angle A to BC and it should be clear that sin(A/2) = (a/2)/b that will give angle A, and then B = C = (180-A)/2

*August 19, 2016*

**physics**

Northeast is E45°N or N45°E. Assuming you mean E60°N, that means <10,0> + <5/2,5√3/2> + <x,y> = <0,0>

*August 19, 2016*

**phisics**

<-150,0> + <0,-50> = <-150,-50>

*August 19, 2016*

**Math**

put all those words into math: j-2 = g+2 j+2 = 2(g-2) Now just solve for j

*August 19, 2016*

**physics**

1/2^5 = 1/32 of the original amount

*August 19, 2016*

**Math**

ever try using math symbols? (ab)^3 / b^2 = a^3b ab^3 / b^2 = ab why? b^3/b^2 = b*b*b / b*b and so two of the b's cancel out

*August 19, 2016*

**math**

the work is what it takes to move the center of gravity of the water's weight the required height. The center of mass is h/2 meters below the top of the tank, so the distance to be moved is h/2 + 4 meters. If d is the density of water, in kg/m^3, then mdg is the weight of ...

*August 19, 2016*

**Pre Calculus**

You have messed up on your last line: F = 150 (√3/2, 1/2) + 75 (−√3/2, 1/2) F = (75√3-37.5√3, 75+75/2) F = (37.5√3,112.5) = 75 (√3/2,3/2) = 75√3 (1/2,√3/2) = 130 at 60°

*August 18, 2016*

**Math**

maybe they are doll pillows, or maybe just pin cushions ...

*August 18, 2016*

**math**

also, which 2?

*August 18, 2016*

**geometry**

where did the cylinder come from? Area grows as the square of the scale. So, 864/384 = s^2/8^2 s = 12

*August 18, 2016*

**Physical Science**

How many significant figures should the product 62.25 * 37.4 have ? a-2 b-3 c-4 d-7 my answer is c or 4

*August 18, 2016*

**Math (Check answers)**

1B (see #4) 2D ok 3C 4B ok 5C you seem to have associative and commutative mixed up

*August 18, 2016*

**Pre algebra**

01.01 ok 01.07 ok 01.03 ok The usual online notation for exponents is ^ 5^4 * 5^-6 = 5^-2 = 1/5^2 all those words are just irritating 01.01 Nope. √81 = 9 01.02 ?? 37^2 * 30 = 41070 (37)2 * 30 = 37*2*30 = 2220 Now sure how you get 314. Maybe your notation is obscuring the...

*August 18, 2016*

**math**

"ased" is what got included from "increased" 1.10 * 0.80 * 1.10 = 0.968 so, it decreased by 3.2%

*August 18, 2016*

**High Agility Math**

for Julian, the counts could be brothers 2 sisters 1 brothers 4 sisters 2 Bingo, because then Maria has 5 brothers and 1 sister

*August 18, 2016*

**Math**

since all the coordinates are positive, it is in the 1st quadrant. If that gave you trouble, you need to review the quadrant stuff.

*August 18, 2016*

**Algebra II**

well, does f(4) = 2? yes. and, your solution of (x+6)/2 is correct

*August 18, 2016*

**Math**

well, the amount used for n washers is 3/32 n + 1/16 (n-1) = 5/32 n - 1/16 since there are only n-1 waste cuts for n washers. So, now you need to find n such that 5/32 n - 1/16 <= 25 1/2 n < 163 3/5 So, 163 washers may be cut

*August 18, 2016*

**math**

do you mean sin(2θ) or sin^2(θ) ? Anyway, if sinθ = 3/5, then cosθ = 4/5 The, if you want sin(2θ) just use your double angle formula.

*August 18, 2016*

**Math**

You have: S3 = 1/2 (S7-S3) 3/2 (24+2d) = 1/2 (7/2 (24+6d) - 3/2 (24+2d)) d = 2 AP = 12,14,16, 18,20,22,24 I'll let you verify the result.

*August 18, 2016*

**science**

There's lots unsaid here. Are A and B on the same side of the board? If so, it is unreasonable to expect a 25kg girl to balance the combined 85kg of the other two. You need some more information here, like distances and such.

*August 18, 2016*

**8th grade math**

(p-2.00)*1.20 = 9.00

*August 18, 2016*

**Maths**

subtract the area of the pool from the total area: (40+6)(30+6) - 40*30

*August 18, 2016*

**Science help pleaseeeee?!?!**

You know PV=kT That means that PV/T = k is constant So, you want T (in °C) such that 1.58*2.46/(T+273.15) = 1.05*4.25/(95.0+273.15) T = 47.5°C

*August 18, 2016*

**COMPUTER**

depending on the language, just check s == reverse(s)

*August 18, 2016*

**Maths - Year 10**

draw a triangle. opposite/adjacent is adjacent/opposite for the complementary angle. tan76°/cot16° = tan76° * tan16° = tan76° * cot74° not sure that's any simpler

*August 18, 2016*

**Math**

3 A greater remainder means a larger quotient and a smaller remainder

*August 18, 2016*

**Them**

how many moles N2O5? You get half that many moles of O2

*August 18, 2016*

**Math- Geometric solutions and problems RIA**

no idea what A and B are supposed to mean You need to recognize powers of 2 and simple multiples C: An = x^(4n-2) D: An = x^(2n)/2^n E: An = 2^n(x^n + x^(n-1)) F: An = 64y^2/2^n I: 200*2^n II: 375*4^n III: If the numbers are x,y,z then we have y/x = z/y x+y+z = 70 5y-4x = 4z-...

*August 18, 2016*

**math**

= 3sin(6T)

*August 18, 2016*

**ecuaciones diferenciales**

Just apply the usual D operator for homogeneous equations. See whether you can work it around to the solution provided here: http://www.wolframalpha.com/input/?i=y%27%27%27%2B10y%27%27%2B25y%27%3De%5Ex

*August 18, 2016*

**Algebra**

if y is a function of x, then each value of x has only one value of y. On a graph, no vertical line crosses the curve more than once.

*August 17, 2016*

**math**

looks good to me.

*August 17, 2016*

**math**

so, the first 10 words cost sh 3. Now, how much for each of the other 3 words?

*August 17, 2016*

**math**

first step: count the words! Then apply the rates.

*August 17, 2016*

**math**

YES! It means "absolute value". Did you not read what I wrote? That's the definition of absolute value. |10| = 10 |-3| = 3 |-12| = 12

*August 17, 2016*

**math**

as always, |x| = x if x >= 0 |x| = -x if x < 0 so, is 12 positive or negative?

*August 17, 2016*

**math**

ok - you are right. So add the area of the base. Geez...

*August 17, 2016*

**math**

assuming you mean surface of the tank, then that would be the same as the surface area of a 3m-high cylinder of water. So, just use your formula for the lateral surface area of a cylinder.

*August 17, 2016*

**Algebra**

(x + 5x-19)/2 * 18 = 477 find x, the shorter base, then 5x-19, the longer base

*August 17, 2016*

**Math**

well, start keeping track: +5 = +5 +5-1 = +4 and so on

*August 17, 2016*

**Math**

or, -(1/2 + 2) = -2 1/2

*August 17, 2016*

**value**

14/20 * 13/19 * 12/18

*August 17, 2016*

**physics**

measured from the positive x-axis, tanθ = y/x = 20.39/188.61 so, θ = 6.17° That's E 6.17° N or, as a course heading, 83.83°

*August 17, 2016*

**Calc**

you want m such that ∫[0,1] (x-x^2)-mx dx = ∫[0,1] mx dx ∫[0,1] x-x^2-2mx dx = 0 (1-2m)/2 x^2 - 1/3 x^3 [0,1] = 0 1 - 2m - 1/3 = 0 m = 1/3

*August 17, 2016*

**Math- arithmetic**

Note that each row has 6 blocks less than the one before. So, row n has 60-6(n-1)=66-6n blocks. Now just use your values of n.

*August 17, 2016*

**Science**

1 is correct. Trailing zeroes do not count.

*August 17, 2016*

**Calculus**

recall the chain rule if F = f(u) and u is a function of x, then dF/dx = df/du du/dx F'(3) = f'(g(3)-h(3))(g'(3)-h'(3)) = f'(5-4)(3-1) = f'(1)(2) = 10*2 = 20

*August 17, 2016*

**number theory**

2009 = 7^2 * 41 2010 = 2*3*5*67 Now just make k so that when the multiplication is done, all the powers are even.

*August 17, 2016*

**maths**

If the sides are x and y, then 4x+4y = 10 x^2 - y^2 = 5/4 Now just find x and y

*August 17, 2016*

**Analytic geometry**

You have the parabola symmetric to the y-axis y = ax^2+b y(0) = 5 y(150) = 60 Now you can find a and b, and thus y(50)

*August 17, 2016*

**math**

Clearly you have an ellipse with semi-axes a = 5 b = 4 So, c=3 The latus rectum is the line perpendicular to the semi-major axis, through a focus. The semi-latus rectum is b^2/a = 16/5

*August 17, 2016*

**St. Pius X High School**

without loss of generality, we can set it up so that the two unit vectors are along the x and y axes. So, if P = <x,y> <0,1>+<x,y> = <1,0> <x,y> = <1,0>-<0,1> <x,y> = <1,-1> I think you can take it from there, eh?

*August 17, 2016*

**Quadratic Equations**

w(3w+2) = 1496

*August 17, 2016*

**Math, Quadratic Equations**

(20-2w)(16-2w) = .60*20*16

*August 17, 2016*

**math help me out**

b = 1.20a c = 1.30b da = 0.80di e = 0.70da c+e = a+28000 a = di Now just start substituting to find a+di

*August 17, 2016*

**Quadratic Equations, math**

total area: 15*20 If the reduction is x, we have (15-x)(20-x) = 1/2 * 15*20 Now just find x.

*August 17, 2016*

**Physics**

x = 5sin(πt) x" = -5π^2 sin(πt) x" = 5/2 at two times. You can use the graph at http://www.wolframalpha.com/input/?i=sin(t)+%3D+1%2F(2pi%5E2) to see which value to use.

*August 17, 2016*

**Pre Cal**

maybe - what did you get? take a look at http://www.wolframalpha.com/input/?i=(3%2Bi)(5-2i) and put in your numbers

*August 17, 2016*

**Pre Cal**

if you can multiply binomials, you can multiply complex numbers. Start off with (3+i)(5-2i) = 3*5 - 3*2i + 5i - 2i^2 = 15 - 6i + 5i + 2 (since i^2 = -1) = 17-i Now multiply that by (4-7i) and you're done

*August 17, 2016*

**physics**

as you know, v^2 = 2GM/r Now just look up G and Mearth and crank it out.

*August 17, 2016*

**math**

If you construct a Venn diagram, it should be clear that 12+16-x = 21-2

*August 17, 2016*

**science**

write the balanced equation see how many moles of NaCl are required for each mole of H2SO4 convert that to grams of NaCl

*August 17, 2016*

**Physics**

Let the fulcrum be at 60 from the left end. 60g have center of mass 30 to the left 40g have center of mass 20 cm to the right The 80g mass must be on the right side, at a distance x such that 60*30 = 40*20 + 80x so, its location is at 60+x cm from the left.

*August 17, 2016*

**Math**

It might not always be true, but performance will almost certainly not improve if no necessary effort is applied.

*August 17, 2016*

**math**

that would be the total volume divided by the volume required for each child: m^3 ÷ (m^3/child) = child (20*9.5*8)/2.5 = ?

*August 17, 2016*

**math**

given the terms, you must have some ideas, no?

*August 17, 2016*

**math**

1959

*August 17, 2016*

**math**

I can't say I much care for your notation or your grammar, but 4.5*600 + 2*1200 + 3*1500 = 9600 That's how much he spent. So, ...

*August 17, 2016*

**physics question**

recall that range = v^2/g sin(2θ) height = v^2/g sin^2(θ) so, solve for θ an excellent discussion of trajectories for all your problems can be found at https://en.wikipedia.org/wiki/Trajectory

*August 17, 2016*

**Math**

as with all rectangles, the area is length * width. Since both are 13, the area is 13*13 or 13^2

*August 17, 2016*

**algebra**

well it would be 9 times the change in one hour, right?

*August 17, 2016*

**Solid Geometry**

these are all the same problem. The lateral area is just the area of eight identical isosceles triangles, each with base equal to the side of the octagon, and height equal to the slant height of the pyramid, or √(h^2+a^2) where h is the height of the pyramid and a is the...

*August 16, 2016*

**Calculus**

It is certainly easier to integrate over y! Again, we have to distinguish between algebraic and geometric areas, since the curves cross each other at (1,0). So, the area is ∫[-1,0] (-y^3-y^2+1)-(y^3-y+1) dy + ∫[0,1/2] (-y^3-y^2+1)-(y^3-y+1) dy Better double-check ...

*August 16, 2016*

**Calculus**

If you want algebraic area, it is zero, since the sinx curve is above cosx just as much as it is below. See http://www.wolframalpha.com/input/?i=plot+sinx,cosx The geometric area is just twice the area on the interval [-3π/4,π/4], or a = 2∫[-3π/4,π/4...

*August 16, 2016*

**physics math**

√(20^2+5^2) at an angle θ east from south such that tanθ = 5/20

*August 16, 2016*

**math**

such a point will lie on the perpendicular bisector of the line between the two points. Since the slope of that line is 5/2, your point will lie on the line y - 7/2 = -2/5 (x-4) A point on that line with equal x- and y-coordinates will be x - 7/2 = -2/5 (x-4) or, (51/14,51/14)

*August 16, 2016*

**Pre-calc**

another? Why not show how far you get with one of these? Aside from the trig, it's just algebra I: (2sinθ+1)(sinθ+1) = 0 ...

*August 16, 2016*

**Algebara**

BS I can refer you to http://www.homeschoolmath.net/teaching/square-root-algorithm.php

*August 16, 2016*

**Algebara**

you can try trial and error, using closer and closer guesses, or do it by hand. For example, 3^2 = 9 4^2 = 16 so it is between 3 and 4 3.7^2 = 13.69 3.8^2 = 14.44 so you know it is between 3.7 and 3.8 There are many web sites that explain the method of doing roots manually.

*August 16, 2016*

**algebra 1**

3x/12 - 7/12

*August 16, 2016*

**Java programming**

I assume you can do the I/O The calculation is w = (x+y)*z

*August 16, 2016*

**Calculus - Stop the Presses!**

My typo made it wrong. I hope you caught it. Let's pick up at Now let v = 1-u^2 dv = -2u du and your integral now becomes ∫-1/2 √v dv = (-1/2)(2/3)v^(3/2) = -1/3 v^(3/2) -1/3 (1-u^2)^(3/2) = -1/3 cos^3 x + C That's better!

*August 16, 2016*

**Calculus**

Awkward choice, but let u = sinx du = cosx dx ∫sinx cos^2x dx = ∫sinx cosx cosx dx = ∫u√(1-u^2) du Now let v = 1-u^2 dv = -2u du and your integral now becomes ∫-1/2 √u du = (-1/2)(2/3)u^(3/2) = -1/3 u^(3/2) = -1/3 sin^3 x + C Now you just ...

*August 16, 2016*

**Math**

12 1/8 + 6 1/2 = 12+6 + 1/8 + 1/2 = 18 5/8

*August 16, 2016*

**Math**

using what you know about the sum and product of roots of a quadratic, a+b = -m ab = m^2-8 a^2+ab+b^2 = (a+b)^2-ab = m^2-(m^2-8) = 8

*August 16, 2016*

**Math halp plz**

try making them decimals -5/6 = -0.833 -5 = -5.00 -√26 = -5.099 -31/6 = -5.166 now what do you think? If in doubt, mark them on a number line.

*August 16, 2016*

**perfect number**

see your earlier post then... https://en.wikipedia.org/wiki/Perfect_number

*August 16, 2016*

**perfect number**

you asked this 4 minutes ago. geez - impatient much?

*August 16, 2016*

**maths**

5/6 * 2/3

*August 16, 2016*

**perfect number**

google is your friend. Try https://en.wikipedia.org/wiki/Perfect_number

*August 16, 2016*

**math**

geez - 3 postings in 6 minutes? impatient much?

*August 16, 2016*

**Physics**

PI, not pie!! just plug in your value for r: 4/3 π * 4^3 = 256/3 π mm^3 But 1L = 1000cm^3 = 10^6 mm^3 so, v = 256π/3000 = 0.268L or, you can convert 4mm = 0.4cm first, and then v = 4/3 π * .4^3 = 0.268L

*August 16, 2016*

**algebra**

This is discussed at http://www.artofproblemsolving.com/community/c5h469913p2630559 click on the link that says solution

*August 16, 2016*

**math**

Their relative contributions are in the ratio 5:6, so divide the profits similarly.

*August 16, 2016*

**PreCalc**

2.4340 = π - .7076 sin(x) is positive in QI and QII

*August 15, 2016*

**Algebra**

I'll do one; you try the others. True or false? Negative numbers are closed under addition. True: for any positive a,b -a + -b = -(a+b)

*August 15, 2016*

**maths**

so, did you draw and label the Venn diagram yet? It should be clear that the number of students is 20+13-8+9

*August 15, 2016*

**Math**

A = k∛P no idea what Q is, unless it is a typo. If A = 2/3 when P=8, then 2/3 = k∛8 2/3 = 2k k = 1/3

*August 15, 2016*