Sunday
February 7, 2016

Posts by steve

Total # Posts: 37,460

anty alice
type you equation in at wolframalpha.com
February 4, 2016

math
Draw a diagram. The slant height is s = 42/cos30°
February 4, 2016

maths
check the intercepts. when x=0, y=b when y=0, x=a so, you have a right triangle with legs a and b, so its area is ab/2
February 4, 2016

Calculus
If the angle is x, then you have a trapezoid with lower base 4", and upper base 4+2*4cosx, and height 4sinx. So, the area of the cross-section is a = (4 + (4+8cosx))/2 * (4sinx) = 16 sinx (1+cosx) da/dx = 16(2cos^2(x)+cos(x)-1) = 16(2cosx-1)(cosx+1) da/dx=0 when cosx = 1/...
February 4, 2016

circumference...math
recall that the circumference of a circle of diameter d is C = πd
February 4, 2016

Math
vertical angles are equal, so 7x+7=112 x=15 you are correct.
February 4, 2016

math
solve for t with e^(.10*t) = 2
February 4, 2016

math
the small gear turns 4 times as fast as the large one.
February 3, 2016

Math
looks ok to me.
February 3, 2016

maths
well, here's the graph: http://www.wolframalpha.com/input/?i=%282^x%29%28cot+x%29%2Fx^1%2F2 did you have some question about it?
February 3, 2016

MATH
well, a = 8 r = 3/4 Tn = 8 * (3/4)^(n-1)
February 3, 2016

Calculus
what is the height of the tank? You need to know how far above the top of the oil is the spout, and how deep is the oil. Anyway, assuming the oil has a depth of d meters, and the spout is h meters above the top of the oil, then consider the oil as a stack of thin slices of ...
February 3, 2016

Calculus
a = dv/dt, so v(t) = 2t^3 = 2*6^3
February 3, 2016

Calculus
all look ok to me. good work.
February 3, 2016

calculus 1
clearly the limit is (8+1)/(6-4) = 9/2 Not sure what your definition 2 is, but if you need to find δ such that |f(x+δ)-9/2| < 0.5 then that means |(4(2+δ)+1)/(3(2+δ)-4)-9/2| < 0.5 Work your way through that and you will find that δ < 0.125 So...
February 3, 2016

Math
(a) stretch by 2 and shift up 3 (b) shift left 1 and down 3 (c) shrink by 2 and reflect in x-axis (d) shift left 1, reflect in y-axis, reflect in x-axis, shift up 3. Just plug in your numbers to find the image of the point.
February 3, 2016

Geometry
22+16-32 = 6 So, there are 6 juniors who do both. P(both) = 6/50 = 3/25
February 3, 2016

Math
assuming you have a hemisphere atop a cylinder, they both have the same radius. So, just plug your numbers into the usual volume formulas.
February 3, 2016

Math
clearly y is discontinuous at x=0, since lim(x->0-) = 3 lim(x->0+) = 1 y'=-2x for x<0 y'=2x for x>0 y" = -2 for x<0 y" = +2 for x>0 so, y is increasing everywhere, since y'>0 everywhere it is defined. y is concave down for x<0 y is...
February 3, 2016

Writing equations to represent situations
x = 17 xy = 680 2(x+y) = ?
February 3, 2016

Math
1: probably a trapezoid 2: Must mean that there are two such congruent sides, not that all pairs are congruent. Might be a trapezoid or a kite. 3: could be a rectangle or trapezoid. Diagonals of a rhombus are not equal. 4: general quadrilateral. Try drawing one 5: kite Try ...
February 3, 2016

Math
well, there are 57/y bananas That means there must be only 57/y apples, so the result will be 57/y oranges, each having mass x+y so, the mass of oranges will be 57(x+y)/y = 57(1+x/y) grams
February 3, 2016

Math
as always, swap variables and solve for y: 3x+5y=18 5y = 18-3x y = (18-3x)/5 Did the other one in your previous post (see related questions below)
February 3, 2016

Math
I think you are missing something. Each added triangle has a smaller area and a smaller perimeter. I think I am missing something, too. If all the triangles are inscribed into the same area, the total area is unchanged, right? By "the perimeter" do you mean the sum ...
February 3, 2016

math
y = 144+(115.2-144)/(14) x = 144-2.057x Now just plug in values for x.
February 3, 2016

Algebra
(6x^-2)^2 = 36 x^-4 (1/2 x)^4 = 1/16 x^4 multiply and you get 36/36 = 9/4 = 2.25 If you want us to analyze your work, you need to show it!
February 3, 2016

algebra
if there are all positive exponents, then it is a polynomial. Terms are separated by +/- signs, so just count the terms to determine the type. Add the exponents in each term; the highest sum is the degree of the polynomial.
February 3, 2016

science/maths
divide those time values by 60, since they are in minutes, not hours.
February 3, 2016

Algebra
If the slow plane's speed is x mi/hr, then since distance=speed*time, 4x + 4(x+65) = 2660
February 3, 2016

Algebra
f◦g = f(g) = 3/(g-3) = 3/((2/x)-3) = 3/((2-3x)/x) = (3x)/(2-3x) It looks like the domain of f◦g is all reals except x=2/3, but we also have to exclude x=0, since g is not defined there.
February 3, 2016

math
it is just the product of the two primes, since there are no common factors.
February 3, 2016

maths
review the definition of cot(x). Draw a diagram and you can see that h*cot45 - h*cot60 = 100
February 3, 2016

math
Take a look at this site to see a very similar problem: https://www.quora.com/If-2f-x-3f-left-frac-1-x-right-+-x-2-then-f-2
February 3, 2016

Algebra
y(t) = y(x(t)) = ln(2*4e^(t/2.5)) = ln(8) + ln(e^(t/2.5)) = ln8 + t/2.5 ≈ 0.4t + 2.08
February 3, 2016

Math
what you have is an ellipse with semi-axes of 30 and 20 ft, with the long axis horizontal. So, if the center is placed at (0,0) the equation is x^2/30^2 + y^2/20^2 = 1 So, the upper arch is y = 4/9 √(900-x^2) Now just plug in your various values for x to find the height y.
February 3, 2016

Math
4z-6u
February 3, 2016

math
1 degree of latitude is approximately 111 km. So, 500km south takes you to 50-500/111 = 4.5°N Naturally, the longitude has not changed.
February 3, 2016

math
3(m-5)=6m-60 3m-15 = 6m-60 3m=45 m=15 check: 3*(15-5) = 30 = 6*15-60
February 3, 2016

Michael
probably infinitely many, but the smallest is 1729 = 1^3 + 12^3 = 9^3 + 10^3 as G.H. Hardy learned from Ramanujan.
February 3, 2016

maths
Hint - think of a 5-12-13 right triangle.
February 3, 2016

singaporean math ratio
3/7 spent leaves 4/7 1/4 of 4/7 is 1/7, so 3/7 left 3/7 x = 120
February 3, 2016

math
clearly, that would be 20/50
February 3, 2016

math
Nope. 30 are boys.
February 3, 2016

geometry
This is discussed here: https://en.wikipedia.org/wiki/Semiperimeter
February 3, 2016

Numerical Analysis
well, I don't know what a has to do with x, but pull out your calculator, or use one of the many online calculators, and you can easily learn that tan(1.7) = -7.7 That would have been a lot faster than posting a question like that and having to wait for an answer.
February 3, 2016

Math
(1/2)(h-2)(h) = 60 Now just solve for h
February 3, 2016

Math
200+49*2
February 3, 2016

Science
well, the water was 480 g, so that's 480mL.
February 3, 2016

ACT Prep
points so far: 72+94+85+83+97 = 431 points needed: 6*88 = 528 Points needed on 6th exam: 528-431 = 97
February 3, 2016

math
width=w length=2w-8 2(w + 2w-8) = 194
February 2, 2016

Math (precalculus)
Let the rectangle have width x and height y=33-3x^2 clearly the area is a = xy = x(33-x^2)
February 2, 2016

math
so, list them all: 1,1 1,2 ... 5,4 5,5 Now -- how many of them have matching spins?
February 2, 2016

Geometry
that would be (-3,1) + (11+3,9-1)/4 = (-3,1)+(7/2,2) = (1/2,3)
February 2, 2016

Math
looks good.
February 2, 2016

Math Need Immediate Help????
how can f(x) include y? h = -4.9(t+3)^2+45.8 h^-1 = √((45.8-t)/4.9)-3
February 2, 2016

differential equations
what's the trouble? Expand the right side and you have dS/dt = k/MN (-S^3 + (M+N)S^2 - MNS) That's just a polynomial, which you can easily integrate to find S(t)
February 2, 2016

Calculus(PLZ HELP)
just check out the volume of a spherical cap: http://mathworld.wolfram.com/SphericalCap.html
February 2, 2016

precal
arctan(3/4) ≈ 37° P is in QIV, so θ = -37° or θ = 360-37 = 323°
February 2, 2016

Math/Algebra
since time = distance/speed, d/36 + d/48 = 7/2 4d/144 + 3d/144 = 504/144 7d = 504 d = 72 mi
February 2, 2016

math (factorising by grouping )
skill comes from experience. Just look for common factors. 2ax-6bx+ay-3by You have a 2and a 6, and a 1 and a 3. So, 2x(a-3b)+y(a-3b) (2x+y)(a-3b) Now you try the others.
February 2, 2016

Calc II
best to use discs of thickness dx. So, v = ∫πr^2 dx where r = 6-y. So, v = ∫[-π/2,5π/2] π(6-(3sinx+3))^2 dx = 81π^2/2
February 2, 2016

Pre-Calc
Unless they say something, I'd assume QI. In that case, sinθ=5/13 and cosθ=12/13 sinx=3/5 and cosx=4/5 cos (θ+x) = (12/13)(4/5)-(5/13)(3/5) = 33/65 Usually they specify a quadrant if they want to make you determine the sign of the quantities involved.
February 2, 2016

Math
no formula -- just write down the facts: If pants cost p and shirts cost s, then 3s+2p = 85.50 3s+4p = 123.00 You can now solve for s and p.
February 2, 2016

MATHS
NOTE THAT Y=11-3X NOW USE THAT IN THE 2ND EQUATION!! 2X-(11-3X) = 4 NOW YOU CAN FIND X, AND THEN Y!! CAN YOU HEAR ME? AM I SHOUTING LOUD ENOUGH???!!
February 2, 2016

Pre-Calc Answer Check
right on both.
February 2, 2016

Language
Looks like A or B to me. Two enemies are mentioned, but the eight mentions of quickness and the final friendly offering make me prefer A.
February 2, 2016

Math
try the addition formulas: 3 cos (ωt + 2) = 3(cosωt cos2 - sinωt sin2) 4 sin(ωt+1) = 4(sinωtcos1 + cosωtsin1) adding them up you get 3cosωtcos2+4cosωtsin1 + 4sinωtcos1 - 3sinωtcos2 Now, according to wolframalpha.com, that gives...
February 2, 2016

Math help please
9:7
February 2, 2016

algebra
x+y=5 2x+y=2 Now just solve for x and y
February 2, 2016

eglish
at least the sentence is correctly written.
February 2, 2016

Math
#1 ok #2 not quite #3 nope. See all those 9's?
February 2, 2016

SO HARD! MATH
First, decide whether you are going to stack them on their faces, or on their edges.
February 2, 2016

algebra
2(a-3) = b+3 a+5 = 2(b-5) A has $11, B has $13
February 2, 2016

Math Help
No diagram, but probably A, if the two form a straight line.
February 2, 2016

chemistry
write the balanced equation, then compare ratio of the number of moles of each.
February 2, 2016

algebra
If the woman is w, and the son is s, then we know w-7 = 4(s-7) w+7 = 2(s+7) woman is 35, son is 14
February 2, 2016

math
doesn't look like one to me. It's an equation.
February 2, 2016

mathematics extension
not sure. What was the question? distance from start? bearing from start to finish? Name of pilot?
February 2, 2016

Math
well, the slope is undefined; the line is vertical. So, the line is x=5 The line y=11 has zero slope. So, the line through (2,-5) is y = -5
February 2, 2016

Maths
y = x(x+4) The roots are at 0 and -4, so the vertex is at -2. see http://www.wolframalpha.com/input/?i=x^2+%2B+4x
February 2, 2016

math-Polya
not sure about Polya, but the maximum-area quadrilateral is a square. as for the circle, since c = 2πr and A = πr^2, A = c^2/(4π)
February 2, 2016

Math
The total points are not 13, but 35+10 = 45. So, using x,y,z for the scoring plays in the same order as described above, 6x+y+3z = 45 x = y x = 6z You certainly don't need elimination for this, since the substitutions are so easy.
February 2, 2016

algebra
since v = Bh, you have 264 = 48h ...
February 1, 2016

Calculus
First off, the equation should be (f(x+h)-f(x-h))/(2h) if f(x) = a(x-b)^2+c, then f(x+h) = a(x-b+h)^2+c f(x-h) = a(x-b-h)^2+c f(x+h)-f(x-h) = a((x-b +h)^2 - (a-b -h)^2 = 4ah(x-b) divide that by 2h and you have 2a(x-b) Now, f'(x) = 2a(x-b) ta-daa
February 1, 2016

Precal
enter your coefficients here: http://www.gregthatcher.com/Mathematics/GaussJordan.aspx
February 1, 2016

math
well, if you got 100% on all your tests, that would account for 70% of your grade. So, you'd then need at least 33.3% on the homework. But, if you scored 100% on all the homework, that would account for 30% of your grade, so you'd need 71.43% on the tests. So, the ...
February 1, 2016

More math
all correct. good work.
February 1, 2016

Math
if there are c chickens, then there are 40-c cows. So, adding up the legs, 2c + 4(40-c) = 100
February 1, 2016

Do I have enough time
Don't forget that you will have to spend a half hour correcting your spelling and grammar, too!
February 1, 2016

Math
If I read your language correctly, there is a 5m border around the field. So, if the dimensions of the whole area is 130x85, then the field is 120x75.
February 1, 2016

Math
as usual, k∘d = k(d) = √(d^2+100) = √((35t)^2+100) assuming t is in hours.
February 1, 2016

math
NO! Read we wrote!!! The sides are 9 over √2
February 1, 2016

math
If the diagonal is d=x√2, then x = d/√2 you did d*√2 instead.
February 1, 2016

Biology
Wine is made by mixing yeast with grapes and allowing the yeast cells to undergo fermentation. Sparkling wine is a type of wine that contains high levels of dissolved carbon dioxide. What is the source of the carbon atoms in the carbon dioxide found in sparkling wine? ethanol ...
February 1, 2016

Biology
I'm sorry I meant c
February 1, 2016

Biology
What would most likely happen to cells placed in fresh water? a- water would flow out because they are hypotonic to the external environment b- water would flow into them because they are hypotonic to the external environment c- water would flow out of them because they are ...
February 1, 2016

math
assuming you want integer values, just find the factors of 389 Hmm. 389 is a prime number. So, just pick any value (x) for the width and the length is 389/x. I suspect a typo.
February 1, 2016

chemistry
HCl + NaHCO3 = NaCl + H2O + CO2
February 1, 2016

Math
That is correct.
February 1, 2016

Geometry
4(1)-4(-1)+2 = 4+4+2 = 10 ??
February 1, 2016

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