Tuesday

July 26, 2016
Total # Posts: 42,093

**physics**

How long does it take the bomb to fall 8000m? 4.9t^2 = 8000, so t=40 s In 40s, the bomb will travel 8000m. What a coinkidink! So, the angle is just 45°
*July 12, 2016*

**math**

just solve 3x + 1/2 x^2 = 8
*July 12, 2016*

**pre cal**

splashdown occurs when h=0 max height is at t = -b/2a = 115/9.8
*July 12, 2016*

**agebra**

well, if you know the mean and the std, µ-2σ <= x <= µ+2σ
*July 12, 2016*

**math**

dy/dx = xy dy = xy dx dy = 1*2 * 0.4 = 0.8
*July 12, 2016*

**pre cal**

recall that the vertex of a parabola is at t = -b/2a so evaluate h(t) there.
*July 12, 2016*

**maths**

Just change the numbers in Reiny's solution here: http://www.jiskha.com/display.cgi?id=1455402753
*July 12, 2016*

**pre cal**

well, the diagonal of the square is the diameter of the circle...
*July 12, 2016*

**pre cal**

The time it takes for the sound to come back is d/c The time it takes to fall a distance of d is found using h0 + v0 t - g/2 t^2 = d Solve that for t, and then you have t = 1/g (v0 + √(v0^2 - 2g(d-h0))) Now you know that 1/g (v0 + √(v0^2 - 2g(d-h0))) + d/c = t Now ...
*July 11, 2016*

**Algebra/Calculus**

note that (x+y)^2 = x^2+2xy+y^2 x^3 + y^3 = (x+y)(x^2-xy+y^2) Now just plug in what you know.
*July 11, 2016*

**algebra 2**

3x-15 = 0 when x=5 everything else is ok.
*July 11, 2016*

**algebra 2**

a denominator cannot be zero because division by zero is undefined. For this one, 64 is never zero.
*July 11, 2016*

**Pre-Cal**

recall that tan(x+y) = (tanx + tany)/(1-tanx*tany) so, cot(x+y) = (1 - tanx tany)/(tanx + tany) Now divide top and bottom by tanx*tany sinx(cotx+tanx) = sinx(cosx/sinx + sinx/cosx) = cosx + sin^2x/cosx = (cos^2x + sin^2x)/cosx = secx
*July 11, 2016*

**MATH**

As I said earlier, e^(a+b) = e^a * e^b That means that e^(a+b+c) = e^a * e^b * e^c Now just plug in your values for a,b,c.
*July 11, 2016*

**Pre-Cal**

Looks ok to me. It might be easier to read π/6 + nπ 5π/6 + nπ So, plug in various values of n to get all the solutions in [0,2π) There will be four of them
*July 11, 2016*

**math please help?! studying for test!!**

√(81+x^2) = √(81+81tan^2θ) = √(81(1+tan^2θ)) = √(81sec^2θ) = 9secθ Looks like you need to brush up on your basic trig identities.
*July 11, 2016*

**math help?!**

36-x^2 = 36-36sin^2θ = 36(1-sin^2θ) = 36cos^2θ so, √(36-x^2) = 6cosθ
*July 11, 2016*

**Pre-Cal (Help Plz!)**

so, you got tanθ = ±√3 cosθ = -1/2 tanθ = √3 means θ = π/3 or 4π/3 tanθ = -√3 means θ = 2π/3 or 5π/3 cosθ = -1/2 means θ = 2π/3 or 4π/3 so, that gives nπ + π/3 nπ + 2...
*July 11, 2016*

**Pre Calculus**

Hmmm. I get cosu*cosv - sinu*sinv = (-24/25)(-12/13)-(7/25)(5/13) = 288/325 - 35/325 = 253/325
*July 11, 2016*

**Pre Calculus**

since y>0 and x<0, draw your triangles, and you can see that cos u = -24/25 sin v = 5/13 Now just plug them into your cos(u+v) formula.
*July 11, 2016*

**MATH**

yes, as far as you went. But, if you are using natural logs, log(e) = 1, so the answer is just 5y By definition logbb^n = n b^(logbn) = n because logs and powers are inverse functions, just like √x and x^2 are inverses. Like + and - or * and / It's just that we don&#...
*July 11, 2016*

**MATH**

recall that e^(a+b) = e^a * e^b AND LOSE THAT CAPS!!
*July 11, 2016*

**maths**

"square bracket"? Is your keyboard defective, so you can't just type "[" ? Even more confusing is that you didn't use what I gave you at http://www.jiskha.com/display.cgi?id=1468255629
*July 11, 2016*

**Pre-Cal**

you know that the reference angle is θ = π/3, right? Because cos π/3 = 1/2 Now, since cosπ = x/r, you need x negative, so you are in QII and QIII. So, draw your triangle on the negative x-axis, giving you π-π/3 and π+π/3 = 2π/3 and ...
*July 11, 2016*

**Analytic geometry**

Using what I gave you here: http://www.jiskha.com/display.cgi?id=1468252134 you can surely figure the rest, no? Heck, I even showed you the graph! Where do you get stuck?
*July 11, 2016*

**math**

Not unless 7-1 = 8
*July 11, 2016*

**Math**

If what you have is 0.5(x-2)^2 ------------------- (x+1)(x-5)^3 then you have 0.5(x^2+...) / (x^4+...) which approaches zero for large values of x.
*July 11, 2016*

**pre calculus**

No. You are half right. θ=12x is the right substitution to use, but if θ = 12x, what you have is cos(θ/2) = cos 6x
*July 11, 2016*

**pre calculus**

did you even look up your half-angle formula? It says that cos(θ/2) = √[(1+cosθ)/2] I think the substitution is now clear.
*July 11, 2016*

**maths**

recall that 2 sin x/2 cos x/2, so the equation becomes cos x/2 - 2 sin x/2 cos x/2 = 0 cos x/2 (1 - 2sin x/2) = 0 I think you can handle that, right?
*July 11, 2016*

**math**

but a triangular pyramid does: v = 1/3 Bh Now just plug in your numbers.
*July 11, 2016*

**maths**

you telling me or asking me? Naturally, sin(2x) is not one of your answers, but if you let x = π/10 and you plug that in, I bet it is one of your answers.
*July 11, 2016*

**maths - Oops**

Dang! That is sin(2x) = 2 sinx cosx
*July 11, 2016*

**maths**

look up your formulas. You want 2 sin(a) cos(b) = sin(a+b) cos(a-b) You don't even need the product-to-sum formulas, since your double-angle formula says that cos(2x) = 2 sinx cosx
*July 11, 2016*

**math**

so, did you do it? what did you get? try wolframalpha.com http://www.wolframalpha.com/input/?i=sin+2x+%2B+1.5+cos+x,+0%3Cx%3C2pi
*July 11, 2016*

**Pre Calculus**

you know that sin^2 x + cos^2 x = 1, so when you expand you have sin^2 x + 2 sinx cosx + cos^2 x recall also that sec^2 x = 1 + tan^2 x cos(pi/2-x) = sin(x) So, what do you think?
*July 11, 2016*

**Math**

assuming you mean a parabola, recall that x^2 = 4py has axis x=0 directrix at y = -p latus rectum = 4p So, your equation is (x-2)^2 = 4(y-4) see http://www.wolframalpha.com/input/?i=parabola+(x-2)%5E2+%3D+4(y-4)
*July 11, 2016*

**Math**

If there are x math problems, then we know that (4/5) x + 3 = 53
*July 11, 2016*

**math**

well, we know that the number is between 5500 and 6500 There must be many possibilities: 5579 5588 5597 ... 6497 6488 6497
*July 11, 2016*

**geometry**

the exterior angles of an n-gon add up to 360 degrees.
*July 11, 2016*

**Math**

I can only think of 2 and 14 which work
*July 11, 2016*

**pre cal**

C'mon, this is just Algebra I: f(x) = a(x-41)(x-p)
*July 11, 2016*

**Math**

V = k/P So, PV is constant. You want P such that P*160 = 30*240
*July 11, 2016*

**math**

clearly the plant grows at 1/2 cm/week So, you have a slope and a point (0,2) ...
*July 11, 2016*

**pre cal**

for x not -1 or 1, put it all over a common denominator, and you have 3x^2-2x-3 = 0 I'm sure you can handle that.
*July 11, 2016*

**Math**

63 <= 2(w + w+4) <= 95 63 <= 2(2w+4) <= 95 63 <= 4w+8 <= 95 55 <= 4w <= 87 13.75 <= w <= 21.75 so, the maximum width is 21 That makes the max length 25
*July 11, 2016*

**pre cal**

or, just factor it: (√x-2)(2√x-1) = 0 √x = 2 or 1/2
*July 11, 2016*

**chemistry**

First balance the equation. The product has a ratio of 1:3 for the atoms. So, 2Cl2 + 6Fl2 = 4ClF3 convert to moles of each reactant The one with the lesser no. of moles needed will limit the reaction. Then figure how many moles of product are produced, and go back to grams.
*July 11, 2016*

**MPA**

so, did you do some searches? geez, you can do that at least, right?
*July 11, 2016*

**chemistry**

so, do you know what reaction yield means?
*July 11, 2016*

**Maths Year 10 Equations**

c(x) = 2100/x s(x) = c(x)+8 = 2100/x + 8 extra credit: how much money did he make on the sales?
*July 11, 2016*

**math**

surely you can see that T(k) = 20+5k
*July 11, 2016*

**Calculus**

well, surely you must in fact have done some work. rather than mumble some excuses, why not show what you did? Then we can analyze it for accuracy and presentability. The critical numbers are where f'(x) = 0 or f'(x) is undefined. So, what does that give you?
*July 11, 2016*

**Calculus**

to find the absolute max/min, you need to check for local extrema in the interval. Then check f(x) at the ends of the interval to see whether they qualify as being more max/min. f'(x) = 2/∛(x-2) clearly that is never zero, so there are no internal local extrema. So, ...
*July 11, 2016*

**maths**

well, come on. How many pairs of digits are there that add to 9? Also, you know that the first digit is greater, since reversing the digits makes a smaller number.
*July 11, 2016*

**Physics**

Recall that the range is r = v^2/g sin(2θ) so, plug in your numbers and solve for θ.
*July 10, 2016*

**math,maths**

(x+2)/x >= 1/5 If x>0, x+2 >= x/5 4x/5 >= -2 x >= -5/2 So, x > 0 If x<0, x+2 <= x/5 4x/5 <= -2 x <= -5/2 So, x <= -5/2 So, in interval notation, x is in (-∞,-5/2]U(0,∞)
*July 10, 2016*

**Math**

p(x) = 9x - (3x+4700)
*July 10, 2016*

**Math**

Draw a Venn diagram. It is clear that 800-(400+240-B&S) = 160+B&S = 200 B&S = 40
*July 10, 2016*

**Math**

40min * 1hr/60min * 69mi/hr * 1gal/23mi = 2 gal
*July 10, 2016*

**Assembly language**

so, what have you done so far?
*July 10, 2016*

**Maths**

Your answer is correct, but where did that 10 come from in the line above it?
*July 10, 2016*

**Pre-Calculus 11**

yes -∛54 = ∛-54 Did you try your answer for the other one?? (2/3)^2-5 is negative. so its square root is not real 3-x = √(x^2-5) 9-6x+x^2 = x^2-5 6x = 14 x = 7/3 Let's try 7/3 3 - 7/3 = 2/3 √(49/9-5) = √4/9 = 2/3 Check the graphs at http://www...
*July 10, 2016*

**science**

Since KE = 1/2 mv^2, you just plug in your numbers to get the energy in Joules: 1/2 * 70.0 * (1000m/10s)^2
*July 10, 2016*

**science**

Set up your balanced equation. How many moles in 11.2g of lime? Use the equation to figure the moles used Convert that to grams
*July 10, 2016*

**physics**

As you recall, the range of such a trajectory is v^2/g sin2θ now just plug in your numbetrs and solve for v
*July 10, 2016*

**sarangz**

60 km/hr = 16.67 m/s So, the acceleration is -16.67m/s -------------- = -1.67 m/s^2 10s Since F = ma, now you can find F
*July 10, 2016*

**science**

Since v = λf just plug in your numbers
*July 10, 2016*

**math**

If you assume 360 days per year, the interest per day is just 1/360 of the annual interest. So, you will be charged 500.00 * 0.18/360 * 364
*July 10, 2016*

**Pre-Calculus 11**

Been there, done that: http://www.jiskha.com/display.cgi?id=1468110223 b=6
*July 9, 2016*

**Pre-Calculus 11**

I assume you want to simplify 5/7 √(3/2) = 5/7 √(6/4) = 5/7 * 1/2 √6 = 5/14 √6
*July 9, 2016*

**Math**

you give the function some input. It applies the rule to the given value. It produces a value as an output.
*July 9, 2016*

**Math**

1200 + 9000 = 10200 so, what do you think? unless you meant 1209 thousands = 1,209,000
*July 9, 2016*

**Maths**

The co- in cosine, cotangent, cosecant means "of the complementary angle." csc(90-θ) = secθ always
*July 9, 2016*

**Maths - Reiny did it right**

sorry. I misread the question.
*July 9, 2016*

**Maths**

as usual, draw the triangle -- in this case in QI. sinθ = y/r cosθ = x/r
*July 9, 2016*

**weber state university**

when an action is to be completed in the future. For example, By noon I will have eaten six doughnuts. By the time you read this post, you will have already figured it out. The FP tense is formed by will + have + past_participle Never mind the distinction between "will&...
*July 9, 2016*

**geometry**

most likely a rectangle, if the cuts are made parallel to the sides
*July 9, 2016*

**Trigonometry**

No spherical trig here. The balloon problem might have qualified, but it says "level ground." (a) tanθ = 5/4 (b) review your tangent function. If the balloon travels a distance d, then d = 110 tan31°50' - 110 tan19°20'
*July 9, 2016*

**Maths**

did this yesterday: http://www.jiskha.com/display.cgi?id=1467998179
*July 9, 2016*

**Math**

The line segment touches bot the x- and y-axes at all times. So, the point p is 3 units away from the x-axis, along the line. So, let the line make an angle θ with the x-axis (measured clockwise). Then picture point P as being at the end of a rod of length 7, which slides...
*July 9, 2016*

**math**

20-6-5 = 9 P(yellow) = 9/20
*July 9, 2016*

**math**

well, 5^2 = 25
*July 9, 2016*

**discrete math**

(g◦f) = g(f) = f^2-2 = (2x+1)^2-2 (f◦g) = f(g) = 2g+1 = 2(x^2-2)+1 x=4f/(2f-1) 2xf-x = 4f f(2x-4) = x f = x/(2x-4) So, the range of f is all reals except x=2. The domain is all reals except 2 and 1/2. The domain of f^-1 is the range of f. The range is all reals ...
*July 9, 2016*

**number magic(math)**

The length plus the width = 6 so, how many pairs of integers add up to 6? If you are not restricted to integer values, then there is no limit to how many you can draw.
*July 9, 2016*

**math**

usually quantities are not negative values, right?
*July 9, 2016*

**algebra**

Add: x-2y+3z = 7 -x+y-2z = -4 --------------- -y+z = 3 Add #2 and 4*#3: 4x+5y+z = -1 -4x+4y-8z = -16 ------------------- 9y-7z = -17 Now you know that z = y+3,so 9y-7(y+3) = -17 9y-7y-21 = -17 2y = 4 y = 2 so, z = 5, x = -4
*July 9, 2016*

**Maths**

same as always: clear the fractions to get nr = (r+20)(n-10) nr = (r-4)(n+10) nr = nr + 20n - 10r - 200 nr = nr - 4n + 10r - 40 20n-10r = 200 4n-10r = -40 or, 2n-r = 20 2n-5r = -20 So, r = 2n-20 2n-5(2n-20) = -20 2n-10n+100 = -20 -8n = -120 n = 15 so, r = 10 15 students share ...
*July 8, 2016*

**Maths**

If each of n students gets r rupees, nr/(n-10) = r+20 nr/(n+10) = r-4 Now just solve for r and n.
*July 8, 2016*

**Math**

there is no average cost. The cost of the items does not change. 3s+8c = 29 8s+3c = 15 11s+11c = 44 Multiply by 2/11 and you have 2s+2c = 8
*July 8, 2016*

**Chemistry**

convert each to moles. Write the balanced equation. The reagent with the smaller moles used will limit the reaction. So, figure the moles produced, and convert back to grams.
*July 8, 2016*

**Math**

well, x is 4, so just substitute 4 for x and evaluate, to get y. y = 2*4+3
*July 8, 2016*

**Maths**

3/2 (2a + 2d) = 48 (a)(a+2d) = 252 a = 16-d, so (16-d)(16-d + 2d) = 252 Now just solve for d
*July 8, 2016*

**Algebra**

h+2s = 5.40 3h+s = 8.70 Now just solve for h and s.
*July 8, 2016*

**Science**

You need 0.1 moles for 1L of diluted acid. The concentrated acid has 1.15 moles per liter. So, you need 0.1/1.15 = 0.087 liters of the concentrate. or, 87 ml
*July 8, 2016*

**English**

how can one letter indicate an order?
*July 8, 2016*

**Science**

h/(500*15) = 1/2 Review the properties of a 30-60-90 right triangle.
*July 8, 2016*

**discrete math**

Get out your atlas and look them up. (c) Miri is located in Sabah false, since both are cities in Malaysia
*July 8, 2016*