Wednesday

August 24, 2016
Total # Posts: 42,741

**trigonometric**

As always, draw a diagram. If the tree has height h, then (61-h)/44 = tan 36°
*August 7, 2016*

**Calc**

f(x) = x^2+(1000-x)^2 = 2x^2 - 2000x + 1000000 f' = 4x - 2000 f'=0 at x=500 f' < 0 for x < 500, so f is decreasing f' > 0 for x > 500, so f is increasing so, f(1000) > f(998) because f is increasing at that point
*August 7, 2016*

**calculus**

well, you know that cos(x) = 1 - x^2/2! + x^4/4! - ... so, cos(x^2) = 1 - x^4/2! + x^8/4! - ... Now just multiply that by x. See http://www.wolframalpha.com/input/?i=x+cos(x%5E2)
*August 7, 2016*

**Calculus with analytic geometry**

all polynomials have a domain of (-∞,∞) Rational functions do too, except where the denominator is zero. So, f(x) has a domain of (-∞,1)U(1,∞) Near x=1, 2x^2-8 is near -6. So, for x<1 y->∞ x>1 y->-∞ So, f(x) has a range of (-&#...
*August 7, 2016*

**algebra**

is there a question in there somewhere? If you think about it a bit, you probably can figure it out.
*August 7, 2016*

**Math calculus**

v = s^3 dv/dt = 3s^2 ds/dt now just plug in your numbers.
*August 7, 2016*

**Physics**

as usual, rms is peak/√2
*August 7, 2016*

**math**

just subtract 3 from 10.
*August 7, 2016*

**math**

1007544
*August 7, 2016*

**Maths**

see related questions below
*August 7, 2016*

**math**

24P2
*August 7, 2016*

**math**

S5 = a(1-r^5)/(1-r) = 44 S10 = a(1-r^10)/(1-r) = 44 - 11/8 now divide (1-r^10)/(1-r^5) = (44 - 11/8)/44 If that looks tough, note that the numerator is a difference of squares.
*August 7, 2016*

**Maths**

for the dinners, m = 2r adding in the desserts, get the total: m + 11 + r + 11+3 = 75 now just solve for r and add in the $14 for dessert. I suspect a typo, since the answer isn't what I'd expect. Of course, the typo might be mine . . .
*August 6, 2016*

**Maths @MyBad**

As usual, Maestro Reiny had the right of it.
*August 6, 2016*

**Maths**

so, it's a typo. Surely you can fix it and continue with the steps.
*August 6, 2016*

**math**

recall how to find the vertex of a parabola. In this case, that will be at x = -b/2a = 500/0.1 Now use that to find P(x)
*August 6, 2016*

**math**

just add up the interest in the parts. It must equal the whole amount specified. If $x is at 3%, then the rest (9000-x) is at 4%. So, .03x + .04(9000-x) = 320
*August 6, 2016*

**math**

as discussed in Method III here, http://jwilson.coe.uga.edu/emt668/EMAT6680.2000/Lehman/emat6690/trisecttri's/trisect.html your point D will be the centroid of ABC. To find the centroid, read here: http://www.mathopenref.com/coordcentroid.html
*August 6, 2016*

**algebra 2**

And, I can spell!
*August 6, 2016*

**algebra 2**

mean 20 20 range 10 15 20 25 median 22 15 15 22 23 25
*August 6, 2016*

**Math**

Since the area is base * height regardless of which base is picked, 27*12 = 36*h where h is the distance between the longer sides.
*August 6, 2016*

**math**

17 cis -61.9°
*August 6, 2016*

**math**

Is the integrand really 1 ------------------------------- (1+e^y)√(1-(x^2+y^2)) ?? I don't think that's doable with elementary functions
*August 6, 2016*

**geometry**

see the prior post http://www.jiskha.com/display.cgi?id=1470476726 if that's you too, stop changing names and wasting time with the same problem.
*August 6, 2016*

**math**

clearly c = 2b b = 2/3 a a+b+c = 180 a + 2/3 a + 2(2/3 a) = 180 a + 2/3 a + 4/3 a = 180 3a = 180 a = 60 so, the angles a,b,c are 60,40,80
*August 6, 2016*

**math**

your third equation is a+b+c = 180 now just solve the system as usual.
*August 6, 2016*

**Science**

any of these look possible? sc he or she carved or engraved it (Lat. sculpsit), namely (Lat. scilicet), salvage charges, scale, scene, science, screw, scruple (weight), sized and calendered, small capitals (printing), supercalendered Read more: http://www.whatdoesthatmean.com/...
*August 6, 2016*

**math**

multiply all the sides by 9/5
*August 6, 2016*

**Maths**

there are lots of online integration calculators.
*August 6, 2016*

**ALGEBRA**

correct
*August 5, 2016*

**trigonometry**

well, you know that sin(x) increases on (-90,90) and decreases on (90,270) So, this one increases where -90 < x-90 < 90 0 < x < 180 and decreases where 90 < x-90 < 270 180 < x < 360 and of course y=0 when sin(x-90) = -3/4 graph is at http://www....
*August 5, 2016*

**math**

what's the trouble? You have the formula; just plug in your values.
*August 5, 2016*

**math**

not sure what's with all the derivatives, but after 10 years he has 6000(1+.01/12)^(12*10) = 6630.75 for the other, we have e^(.07t) = 2 .07t = ln2 t = ln2/.07 = 9.9 years
*August 5, 2016*

**Finance math**

1.1^3 * 1.03 = 1.37093 ∛1.37093 = 1.11089 so, an effective rate of about 11%
*August 5, 2016*

**MATH**

assuming you are giving inside diameters, then the pipe is just a frustrum of a cone, whose base diameter is 30cm. Since the diameter decreased by 10 cm in 500 cm, it will be zero after another 100 cm. So, the volume of the pipe is the volume of a cone base diameter 30 cm and ...
*August 5, 2016*

**math help**

The payment for scheme 1 is: 3700 for 0 <= x <= 50000 3700+.02(x-50000) for x > 50000 so, for various amounts above that, we have 50000: 3700 + 1000 = 4700 100000: 3700 + 1500 = 5200 150000: 3700 + 2000 = 5700 For scheme 2, we have breakpoints at: 50000: .03*50000 = ...
*August 5, 2016*

**math**

if he walked x km, then he rode x+7.95 now add them up so they make the whole distance.
*August 5, 2016*

**physics**

looks good to me
*August 5, 2016*

**maths**

you cannot add up the running balances. Add a few more transactions, and the difference would be even greater.
*August 5, 2016*

**Chemistry**

convert mass to moles and see which reagent limits the reaction. Then compare the 51.0g yield to the theoretical yield using all available materials.
*August 5, 2016*

**math**

as you recall, the parabola ax^2+bx+c has its vertex at x = -b/2a so, plug that in and use that to get part (b)
*August 5, 2016*

**Math**

-50-75+60-45 = ?
*August 5, 2016*

**math help me out**

for x in sales, we have scheme 1: 3700 + .02(x-50000) that works out to 3700 for x <= 50000 3700 + .02x for 50000 < x <= 100000 4700 + .02x for 100000 < x <= 150000 scheme 2: .03x for x <= 50000 1500 + .04x for 50000 < x <= 100000 3500 + .05x for 100000...
*August 4, 2016*

**math**

(7-3×4+6) ok, now what?
*August 4, 2016*

**Math**

start checking after each round after round 1, 500 people remain, numbered 2k+1 after round 2, 250 remain, numbered 4k+1 after round 3, 125 remain, numbered 8k+1 at this point, #1 still remains, but starting with the next cycle, 16k+1, overlap starts to set in 1,17,33,...,993 ...
*August 4, 2016*

**Math**

One thousand people stood in a very large circle. Each starting with the Jennifer Lopez look alike, wore a sign on his or her back with a numeral from 1 to 1000 in a clockwise sequence. They began counting off. The Jennifer Lopez look alike said one in and remained in the ...
*August 4, 2016*

**math**

just set up the inequality. If the other account has x interest, then 3000(.02) + 4000(x) >= 700 60 + 4000x >= 700 4000x >= 640 x >= 0.16 = 16%
*August 4, 2016*

**Pre-Calc with Analytic Geometry**

read the previous two posts and see what you can glean from them. I suspect a name change going on here.
*August 4, 2016*

**Calculus - Need help please**

Well, you know that the principal cycle for tan(x) is from -π/2 < x < π/2 So, now you have -π/2 < π-3x < π/2 -3π/2 < -3x < -π/2 π/2 > x > π/6 or, more usually written, π/6 < x < π/2 But, you ...
*August 4, 2016*

**Help on Pre-Calc**

I assume you can answer the questions for y = tan(x) now just shift the x-values left by π/4.
*August 4, 2016*

**Help Needed for PreCalc**

Did you not read the problem? points on the graph of y=tanx on the interval [π/2,3π] that have a y-coordinate of -1/radical3 geez! y = -1/√3 !! at each of those points. So, knowing the x values, the pairs are (5π/6,-1/√3), ...
*August 4, 2016*

**Help Needed for PreCalc**

well, you know that tan π/6 = 1/√3 using that as your reference angle, and knowing that for a triangle in standard position tan(u) = y/x, you must have either -1/√3 (QII) or 1/-√3 (QIV) So, for the given domain, that means the solutions are x = 5π/6...
*August 4, 2016*

**Pre-Calc help**

again? The period is 2π/4 = π/2 So, divide π/2 into 4 intervals: 0, π/8, π/4, 3π/8, π/2 Now evaluate y at each of those points. I went through a more complete solution earlier - what was not clear?
*August 4, 2016*

**Microsoft exel**

read about merge
*August 4, 2016*

**Arthemetic sequence**

8(a+7d) = 12(a+11d) 8a+56d = 12a+132d 4a = -76d a = -19d So, there are many such sequences: -19,-18,-17,-16,-15,-14,-13,-12,-11,-10,-9,-8 8(-12) = 12(-8) 38,36,34,32,30,28,26,24,22,20,18,16 8(24) = 12(16)
*August 4, 2016*

**Math**

add up the amounts (fraction of the total job) done by them in one minute: 1/90 + 1/m = 1/60
*August 4, 2016*

**Math**

do it as you do with all fractions. Multiply by the LCD. For example, to evaluate 2/3 + 4/7 you multiply by 21. So, here you have 1+(2x)/(x+4)=(3)/(x-1) (1)(x+4)(x-1) + (2x)(x-1) = (3)(x+4) x^2+3x-4 + 2x^2-2x = 3x+12 3x^2 - 2x - 16 = 0 I expect you can solve that one, right?
*August 4, 2016*

**Physics**

s = 1/2 at^2 = 1/2 * 3 * 35^2 v = at = 3 * 35
*August 4, 2016*

**Math**

On the first one, all you are doing is adding 20 to f(x), which just adds 20 to y. So, the graph shifts up 20. Use the point-slope form of the line: y - (-1) = 5(x - (-2)) or y + 1 = 5(x+2)
*August 4, 2016*

**physics**

102g/21cm^3 = 102/21 g/cm^3
*August 4, 2016*

**physics**

correct - an hyperbola
*August 4, 2016*

**physics**

no, you already have meters. You want km. So, you want to divide by m, so they cancel 1m * 1km/1000m = 1/1000 km If you multiply by A, you end up with 1m * 1000m/km = 1000m^2/km which makes no sense
*August 4, 2016*

**math**

Assuming x^2 > x, we have x + x^2 = 1/2 (x^2-x) Of course, if |x| < 1, then x^2 < x, so we have x + x^2 = 1/2 (x-x^2)
*August 4, 2016*

**Math**

actually, that would help if the sum were 4845. In this case, if all three factors were equal, they would be ∛4845 ≈ 17 So, I'd try 15*17*19 = 4845
*August 4, 2016*

**Help needed- PreCalc**

what you really need to know is that the period of cos(kx) is 2π/k. Then just divide that length into 4 intervals, and evaluate y at each dividing point. For example, 3cos(4x+π)+1 has period 2π/4 = π/2. Thus, each quarter has length π/8. So, the points...
*August 4, 2016*

**math**

(a+d)/(a+5d) = 2/5 a+d + a+5d = 28 find a and d, and then S10 = 10/2 (2a+9d)
*August 4, 2016*

**algebra**

4/5 of 300 = 240 so, the gas used is 60/20 + 240/30
*August 4, 2016*

**Math**

y-x = 14 y = 2x+5
*August 4, 2016*

**Math**

5g/1kg = 5g/1000g = 5/1000 = 0.005 = 0.5%
*August 4, 2016*

**Mathematical literacy**

factor out the common 5 all the way across
*August 4, 2016*

**Math**

6 workers do 1 km in 4 days 1 worker does 1 km in 4*6=24 days 1 worker does 3 km in 24*3=72 days 4 workers do 3 km in 72/4 = 18 days or, 1km of road is 6*4 = 24 man-days 3km is thus 3*24 = 72 man-days 72 man-days/4man = 18 days
*August 4, 2016*

**Math**

they add up to 360. Divide 360 into 2+3+4+1=10 parts, and each part is 36. So, the angles are 72:108:144:36
*August 4, 2016*

**Maths**

so, each one is 70° Now you just need to recall that consecutive angles are supplementary. Thus, the other two angles are 110°
*August 4, 2016*

**Math**

well, since area = width * length, 3/(x+2) * 2/(x-3) = 1 6 = (x+2)(x-3) x^2 - x - 12 = 0 (x-4)(x+3) = 0 x = 4 or -3 -3 is no good, since we need positive values for the sides, so x=4. Check: 3/6 * 2/1 = 1
*August 4, 2016*

**Math**

no doubt. Did you try -3/2 ? 3x+2y = 7 2y = -3x + 7 y = -3/2 x + 7/2
*August 3, 2016*

**Math**

r = 7/(3cosθ + 2sinθ) r(3cosθ+2sinθ) = 7 3rcosθ + 2rsinθ = 7 3x+2y = 7 I guess you can handle it from there, yeah?
*August 3, 2016*

**math**

add up the head-count, and the revenue: c+a = 150 11c+16a = 2250 Now just solve for c and a.
*August 3, 2016*

**Precalculus**

first, draw your triangles in standard position. Then it is easy to see that cos(u) = -3/5 cos(v) = 5/13 Then recall your sum formula: cos(u+v) = cosu cosv - sinu sinv now just plug in your numbers.
*August 3, 2016*

**differential equations**

There are several good online R-K calculators. Try one of them. For example, http://keisan.casio.com/has10/SpecExec.cgi?id=system/2006/1222997077
*August 3, 2016*

**geometry**

Since there are 60 minutes in one complete revolution (360°), each minute is 6° So, how many minutes passed?
*August 3, 2016*

**Math**

just find t where (1/2)^(t/5600) = 0.21
*August 3, 2016*

**math**

If it is now x minutes before noon, then it is (4 hours-x min) = 240-x minutes after 8 am. So, 240-x-60 = 3x 180 = 4x x = 45 So, it is now 11:15 That is, 45 minutes before noon One hour ago, it was 10:15, or 135 minutes after 8 am
*August 3, 2016*

**pre cal**

what? posting again in less than 5 minutes? kinda antsy aren't ya?
*August 3, 2016*

**pre cal**

Draw your triangle. It is just a 3-4-5 triangle, so cosα is easy to read off it. Now use the half-angle formula: sin(α/2) = √((1-cosα)/2)
*August 3, 2016*

**Calculus1**

d/dx ∫[e^x,0] sin^3(t) dt = d/dx -∫[0,e^x] sin^3(t) dt = -sin^3(e^x) * d/dx (e^x) = -e^x sin^3(e^x)
*August 3, 2016*

**pre cal**

sin + cos^2/sin = sin + (1-sin^2)/sin = sin + 1/sin - sin^2/sin = sin + csc - sin = csc tan^3 - sec^2tan/cot(-x) = tan^3 + sec^2tan^2 = tan^3 + (tan^2+1)tan^2 = tan^4 + tan^3 + tan^2 = tan^2(tan^2+tan+1) not sure where you want to go with this one sin^4-cos^4 = (sin^2+cos^2)(...
*August 3, 2016*

**Math**

Not much to do here: (4x-2y)/(-2x-y) = 2(2x-y)/-(2x+y) = -2(2x-y)/(2x+y) Now, if there's a typo, and the bottom was -2x+y then you'd have 2(2x-y)/-(2x-y) = -2
*August 3, 2016*

**Math**

well, 70% are boys, right? .70 * 400 = ?
*August 3, 2016*

**Math**

11/2 h - 220 = 145 11/2 h = 365 ...
*August 3, 2016*

**Math**

(x^3+3x^2+2x-5)/(x+1) Might you have a typo? This does not divide evenly
*August 3, 2016*

**Math**

Each zero involves a factor of 10 There are lots more 2's than 5's So, count the factors of 5 in 1-34: 5,10,15,20,25*2,30 = 7 fives, so 7 zeros
*August 3, 2016*

**mathematics**

60% are boys .60 * 1800 = ?
*August 3, 2016*

**science**

2PoP + 3H2O = 2FiZ2
*August 3, 2016*

**pre cal**

The co- in cosine means "of the complementary angle." So, cos(x) = sin(π/2-x) Here, sin(u) = 4/5 Now just recall the formulas for sum of angles, and you get sin(u-π) = -sin(u) cos(u-π) = -cos(u) sin(u-π/2) = -cos(u) cos(u-π/2) = sin(u)
*August 2, 2016*

**calculus**

v = πr^2h = 64, so h = 64/(πr^2) a = 2πr^2 + 2πrh = 2πr^2 + 128/r da/dr = 4πr - 128/r^2 = (4πr^3-128)/r^2 Now set da/dr=0 to find minimum area.
*August 2, 2016*

**math**

add up the pairs of faces 2(x(2x) + x(x+2) + 2x(x+2)) = 63 solve for x. You sure you don't have a typo? Since there are two of each face, I'd expect the area to be an even number, like 64, rather than 63.
*August 2, 2016*

**Ap series**

just use what you know about APs 6/2 (2a+5d) = 46 (a+9d)/(a+29d) = 1/3 solve for a and d, then find a+12d
*August 2, 2016*

**algebra 2**

see http://www.jiskha.com/display.cgi?id=1317927207
*August 2, 2016*

**math**

ummm, 44 and 66 ?
*August 2, 2016*