Wednesday
August 24, 2016

Posts by steve

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
42
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

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