Saturday

October 22, 2016
Total # Posts: 45,159

**math**

tanθ = 191/(4*5280) note that for small angles (in radians) tanθ ≈ θ

*October 19, 2016*

**MATH**

What are you measuring? assign variables for the quantities of interest. What are the constraints?

*October 19, 2016*

**calculus**

sure looks like -4 to me. You had to ask?

*October 19, 2016*

**Trig**

Apparently this is a bizarre attempt to write a fraction. Try using parentheses and virgules, as in (cscθ+1)/(cscθ-1) or something

*October 19, 2016*

**geometry**

draw two adjacent angles. I think the answer will be clear. If not, which statements do you know are true?

*October 19, 2016*

**physics**

The three blocks are accelerated in the amount of a = F/m = 14.3/(1.1+2.72+4.05) = 1.817 m/s^2 They all have that same acceleration. So, since the 1.1kg block is only pushing 2.72+4.05 kg, its force is F=ma Similarly, the last block is pushed with a force of 4.05a N

*October 19, 2016*

**Calc**

looks like ∫[-3,3] ∫[2,19-y] ∫[-√(9-x^2),√(9-x^2)] dy dz dx

*October 19, 2016*

**calculus**

you do need the () around 1/x, since powers are done first, and you don't want (e^1)/x 3+e^(1/x) is never zero, so there are no discontinuities because of a zero denominator. However, since 1/x is undefined at x=0, there is a jump there. lim as x->0- = 5/3 lim as x->...

*October 19, 2016*

**G.p.**

see the related questions below

*October 19, 2016*

**Geometric progression**

Well, you just didn't catch my typo. c*e = (1/3)r^3 * (1/3)r^5 = (1/3)* (1/3)r^8 = (1/3)(432) = 144 So, my correction was wrong. Clearly you did not examine my work to see where the mistake was made. You just threw up your hands and complained I was wrong. Bad form, I must...

*October 19, 2016*

**Geometric progression**

oops. (1/9)(432)

*October 19, 2016*

**Geometric progression**

(a)(ar^8) = a^2 r^8 = 432 c*e = ar^3 * ar^5 = ...

*October 19, 2016*

**A.p.**

If there are n means, then [x,3x] is divided into n+1 intervals. Thus, you have an arithmetic sequence where a = x d = (3x-x)/(n+1) = 2x/(n+1) x, x + 2x/(n+1), x + 4x/(n+1), ... x + 2nx/(n+1), x + 2(n+1)x/(n+1) = x, (n+3)/(n+1) x, (n+5)/(n+1) x, ... 3(n+1)/(n+1) x

*October 19, 2016*

**A.p.**

n/2 (2a + (n-1)d) = 3n^2+2n 2an + dn^2 - dn = 6n^2+4n dn^2 + (2a-d)n = 6n^2+4n d = 6 2a-d = 4, so a = 5 Tp = 5+(p-1)(6) = 6p-1 check: the AP is 5,11,17,23,29,... S1 = 5 = 3*1^2+2*1 S2 = 16 = 3*2^2+2*2 S3 = 33 = 3*3^2+2*3 S4 = 56 = 3*4^2+2*4 ...

*October 19, 2016*

**Algebra**

Just do a long division. Add what you need to make the remainder zero.

*October 19, 2016*

**Math**

3/15 are blue (in math)

*October 19, 2016*

**Maths**

clearly x must be positive for logx to exist. Now, I'm not sure what tools you have at your command for working on this. You could define f(x) = 3x^2-2x^3-log((x^2+1)/x) and find its zeros numerically. Or, if you have calculus available, 3x^2-2x^3 has a single local ...

*October 19, 2016*

**Maths**

I'd say 7 cm, if the map is used to represent the distance AC. I suspect you have garbled the question, since it also lacks some kind of scale indication.

*October 19, 2016*

**math**

consecutive angles are supplementary.

*October 19, 2016*

**Math**

If you use a linear model, when after x years, 38000 + (175000-38000)/20 x = 2(8400 + (168400-8400)/20 x) x = 2.3 So, the price would been double in 1972. So, assume a constant percentage growth each year: 38000 (1+(175/38))^(x/20) = 2(8400(1+(1684/84))^(x/20) x = 12.34 So, ...

*October 19, 2016*

**Help Math**

when cost = revenue

*October 19, 2016*

**Math Help**

this is just about like the one you posted yesterday. How far do you get?

*October 19, 2016*

**Math**

3.14159

*October 19, 2016*

**Math**

28(5/2)

*October 19, 2016*

**Calculus**

note that since tan(x/2) = (1-cosx)/sinx, what you have is f(x) = -tan(x/2)/x = -1/2 tan(x/2)/(x/2) lim(x->0) f(x) is thus -1/2

*October 19, 2016*

**G.p.**

A(1+r+r^2) = 21 A(r^3-1)/(r-1) = 21 A^2 (r^3-1)^2/(r-1)^2 = 441 A^2 (1+r^2+r^4) = 189 A^2 (r^6-1)/(r^2-1) = 441 Now divide and you get to cancel a lot of factors, winding up with (r^2+r+1)/(r^2-r+1) = 441/189 cross-multiply and clean things up, and you end with 2r^2 - 5r + 2...

*October 18, 2016*

**Algebra**

converting Kelvin to Rankine, absolute zero is -459.67°F so, if the temperature drops by 40°F from 80°F, that is a 40/(459.67+80) = .0741 = 7.41% drop That means a corresponding drop in pressure.

*October 18, 2016*

**Calculus**

I plugged in your numbers to Damon's solution and got 40 cm/min What work do you have to show?

*October 18, 2016*

**Calculus**

see related questions below.

*October 18, 2016*

**Math**

11/13 * 10/12

*October 18, 2016*

**Calculus integrals**

I'd start with a long division. The integrand then becomes 8 - 3e^x + e^(2x) - 8/(e^x+1) 8 - 8/(e^x+1) = e^x/(e^x+1) if you let u = e^x+1 du = e^x dx and the integrand is now -3e^x + e^(2x) - 8du/u making the integral -3e^x + 1/2 e^(2x) - 8log(e^x+1) + C

*October 18, 2016*

**math**

draw the triangles in standard position. They are all either 45-45-90 of 30-60-90. Those values you know, right?

*October 18, 2016*

**Maths**

In general, of course, three curves need not intersect in a single point. But, as you say, 2x^2+5x = x^2+4x+12: x = -4 or 3 2x^2+5x = 3x^2+4x-6: x = -2 or 3 x^2+4x+12 = 3x^2+4x-6: x = -3 or 3 So, it looks like (3,33) works fine You messed up in your solution. 6*5 = 30, not 12...

*October 18, 2016*

**MATH PLEASE SHOW WORK**

what work? If the smallest is x, then the next two are x+2 and x+4. So, x^2 + (x+2)^2 = 54+20(x+4) Now just crank it out.

*October 18, 2016*

**Math**

there are many many possibilities. What topic are you studying just now?

*October 18, 2016*

**math please help**

see related questions below

*October 18, 2016*

**math**

pick any number. Multiply top and bottom by that number. For example, 3/30 .17/1.7 and so on

*October 18, 2016*

**Math**

well, 8 + 7 = 15

*October 18, 2016*

**Algebra**

45 is 3/4 of the way from 30 to 50, so 3/4 of the mix will be 50%. Or, more traditionally, 30x + 50y = 45(x+y) 30x + 50y = 45x + 45y 5y = 15x y = 3x So, there is 3 times as much 50% as 30%.

*October 18, 2016*

**Math**

.5*1000 + .25x = 900

*October 18, 2016*

**Mathematics**

(b+5)/(b+2) = 5/4 ...

*October 18, 2016*

**Math**

4/3 * 7/2

*October 18, 2016*

**Math**

no, that's 90% You want .55*120 - .45*120 = 0.10*120

*October 18, 2016*

**Math**

it won 10% more. What is 10% of 120?

*October 18, 2016*

**Math**

P = 2(W+L)

*October 18, 2016*

**Math**

well, 14*3 = 42

*October 18, 2016*

**math**

#7 Nope. The total key sales must be >= 180K #8 Nope. 85 <= (83+91+x)/3 <= 90 #9 Nope. |105 - 35t| = 60 105 - 35t = ±60 #10 First of all, P is not a subset of V. So you are naming the wrong symbol. Your answer appears to be P-V (elements of P not in V) (a) = P...

*October 18, 2016*

**MATH**

No ideas? OK. I'll get you started. As usual, with a diagram. Let's set some labels: S = top of short pole T = top of tall pole C = cable car P = point on ground directly below the car Draw a horizontal line from C which intersects the short and tall poles at Q and R, ...

*October 18, 2016*

**pyhsics**

PE = mgh h = 900-60t

*October 18, 2016*

**Math**

(1-x)/(x-5) + 7x / (x-5)(x+2) ((1-x)(x+2)+7x) / (x-5)(x+2) -(x^2-6x-2) / (x^2-3x-10) Generally one does not talk about "factoring" rational functions. Maybe there was some other operation you had in mind.

*October 18, 2016*

**Physics trajectory**

4.9t^2 = 4.5

*October 18, 2016*

**Math please help**

x^2 + (x+2)^2 = 54+20(x+4)

*October 18, 2016*

**Math**

The sides are 9x and 7x. 2(9x+7x) = 144

*October 18, 2016*

**Math please help**

h(h+1)/2 = 10

*October 18, 2016*

**Math**

jeez! enough with the same problem, already!

*October 18, 2016*

**Math**

adjacent angles add to 180

*October 18, 2016*

**MATH**

Well, I made a boo-boo. Clearly you did not bother to read my work, or you would have found it. I was just as blind, because if the glass empties 10 in. in one hour, clearly the .15 in/hr I got for an answer was way too small. So, it all goes back to this: I swapped y and r in...

*October 18, 2016*

**MATH**

So, what did you try? It'd be nice if you showed your work on the problem. http://www.jiskha.com/display.cgi?id=1476782673

*October 18, 2016*

**Math**

it has decreased by a factor of 3/4 So, it must increase by a factor of 4/3, or up by 33.33%

*October 18, 2016*

**Algebra**

(1-2+4)z + 6

*October 18, 2016*

**math**

just solve x+8 + x+4 + 4x-3 + x^2-3x = 49

*October 18, 2016*

**MATH**

When the man has walked a distance x, his distance d from the pole is d^2 = x^2+30^2 If his shadow then has length s, s/6 = (d+s)/126 or, d = 20s So, plugging that in, 400s^2 = x^2+30^2 at x=40, s = 5/2 800s ds/dt = 2x dx/dt 2000 ds/dt = 80*3 ds/dt = 3/25 When you get stuck, ...

*October 18, 2016*

**Calc**

ok ok I did the first two. See what you can do on these, ok?

*October 18, 2016*

**Maths**

I suspect a typo. There is a mangled character.

*October 18, 2016*

**math**

pi * 2.5

*October 18, 2016*

**Math**

come on. If you are x, what is 5 more than that? what is 5 more than 10? How did you get it? Do the same with x.

*October 18, 2016*

**physics (urgent)**

Read the excellent article at wikipedia: https://en.wikipedia.org/wiki/Trajectory You can then understand why max height = (v sin^2θ)/2g range = (v^2 sin2θ)/2g time in air solves (v sinθ) t - g/2 t^2 = 0

*October 18, 2016*

**math**

The terms grow by 7, so (6293-14)/7 + 1

*October 18, 2016*

**math**

this is just 2(1+2+...+400) So, there are 400 terms. S400 = 400/2 (2+800) Or, you probably know that 1+2+3+...+n =n(n+1)/2 So, your sum is 2* 400*401/2

*October 18, 2016*

**math**

see your other posts. Or, review your material on arithmetic sequences...

*October 18, 2016*

**CALC**

consider the lamina as a collection of thin vertical strips, of height y and width dx. Just add up all the masses. Each strip's mass is its area times it density. If we integrate along x, the density is a constant for each strip. m = ∫[0,1] ρ y dx = ∫[0,1...

*October 18, 2016*

**CALC**

Hmmm. I have to run, but maybe you can figure it out by the time I get back.

*October 18, 2016*

**CALC**

Consider the area as a bunch of tiny rectangles, each of width dx and height dy. Each rectangle's mass is its area times its density. o, adding them all up, using vertical strips so we don't have to split the boundary: m = ∫R ρ dy dx = ∫[0,3]∫[x/...

*October 18, 2016*

**Calculus**

google is your friend. Take a look here: http://mathhelpboards.com/questions-other-sites-52/leprofeces-question-yahoo-answers-minimizing-lateral-area-cone-fixed-volume-8554.html

*October 18, 2016*

**Math**

2 7/12 + 1 5/7 = 2 49/84 + 1 60/84 = 3 109/84 = 4 25/84

*October 18, 2016*

**Math**

equilibrium quantity is where supply = demand: -2x+15 = 5x+1 x = 2 so, p=11 Looks like D to me

*October 18, 2016*

**Math help**

just solve C(x) = R(x) ...

*October 18, 2016*

**math**

425

*October 18, 2016*

**Maths**

c'(x) = 40 + 0.4x c(x) = 40x + 0.2x^2 + k Now plug in your known value of c(0) = 600 c(x) = 600 + 40x + 0.2x^2

*October 18, 2016*

**Differentiation**

yes

*October 18, 2016*

**math**

see http://www.jiskha.com/display.cgi?id=1476803497

*October 18, 2016*

**math**

I have that formula because, as I showed at the very first, the volume starts at 30π ion^3, and drops at a rate of π/2 in^3/min. ----------------------------------- For those who followed a link to get here, ----------------------------------- I swapped y and r in ...

*October 18, 2016*

**math**

v = π/3 * 3^2 * 10 = 30π so, dv/dt = -30π in^3/hr = -π/2 in^3/min When the sand has a depth of y inches, the surface has a radius of r = (3/10) y So, at that point, v = π/3 y^2 r = π/10 y^3 dv/dt = 3π/10 y^2 dy/dt -π/2 = 3π/2 * 6^2 ...

*October 18, 2016*

**Maths**

.24x = 16.2

*October 18, 2016*

**physics - oops**

rats: 5t^2=20

*October 18, 2016*

**physics**

how long does it take to hit the ground? 10t^2 = 20 use that t to find the horizontal distance: d = 15t.

*October 18, 2016*

**MATH**

divide the nut into 6 equilateral triangles, with sides = r. y=r

*October 18, 2016*

**math**

If the ladder has length z, then x^2+y^2 = z^2 x dx/dt + y dy/dt = 0 when dy/dt = -3 dx/dt, x dx/dt - 3y dx/dt = 0 x = 3y Thus, the angle θ is tanθ = 1/3

*October 18, 2016*

**math**

I'll assume you meant that the faster plane is 5 miles farther east... say the slow one is flying along the x-axis, and the faster one along the line y=12. Then at time t hours, the distance z between them is z^2 = (300t - 240t)^2 + 12^2 = 3600t^2 + 144 300t-240t = 5 when ...

*October 18, 2016*

**algebra**

If the regular gas costs x cents/gal, then 5x + 10(x+22) = 6130

*October 18, 2016*

**Please explain**

if you rearrange things a bit, you get 7x-3y = 63 2x+4y = -42 Looks like A to me.

*October 17, 2016*

**PRE-CAL**

cot^2 = csc^2 - 1 use that and it factors easily.

*October 17, 2016*

**6th grade math**

Not really. Draw a figure with any number of sides. Except for a triangle, it can be squashed in various ways, making the area anything from almost zero to a maximum when the figure is a regular polygon. That is why structures are usually based on triangular frameworks -- the ...

*October 17, 2016*

**math**

If there are x liters of the 55%, then the rest (50-x) is 80%. SO, now just add up the acid in the parts -- it must equal the acis in the final mix: .55x + .80(50-x) = .60*50

*October 17, 2016*

**Trig**

I assume you meant (using x) sin3x - sin4x Use the sum-to-product formula: sinA-sinB = 2 cos(A+B)/2 sin(A-B)/2

*October 17, 2016*

**2nd grade math**

1100 1121 1142 1163 1184

*October 17, 2016*

**Calculus**

Consider the function y = -x^2

*October 17, 2016*

**Math**

combine the three heights into a single height. How about some input on your other posts? It begins to look like a homework dump, since most of the problems are very similar.

*October 17, 2016*