# Posts by Steve

Total # Posts: 52,051

**Math**

you have to keep writing an equation; you just dropped off the right side. In any case, remember from your Algebra I that you usually need to set stuff to zero to solve. Now, using the fact that sin^2x+cos^2x=1, 2cos^2x+sinx-1 = 0 2-2sin^2x + sinx-1 = 0 2sin^2x-sinx-1 = 0 (...

**Trig**

oops, sorry Reiny...

**Trig**

Remember your double-angle formulas. You have tan(2*30) = ?3 Reiny dropped the 2 in the numerator...

**Trig**

(1+tan^2x)/tan^2x = 1/tan^2x + 1 = cot^2x + 1 = csc^2x

**laplace transformation:help damon or steve or rein**

In case you don't have an online calculator handy, L{1} = 1/s L{e^t} = 1/(s-1) = F(s) L{t^2 e^t} = (-1)^2 F"(s) = 2/(s-1)^3 L{y} = f(s) L{y'} = sf(s)-f(0) = sf(s)-1 L{y"} = s^2f(s)-sf(0)-f'(0) = s^2f(s)-s+2 L{y'"} = s^3f(s)-s^2f(0)-sf'(0)-f&...

**Bachelor of computer science**

I'm sure you can do the I/O. The calculation is if hours <= 0 print "error - no hours entered" else if hours <= 40 pay = rate * hours else pay = rate*40 + rate*1.5*(hours-40) endif

**math**

make up your mind -- BASIC or FORTRAN ? in any case, find the prime factors of each number, and select all those common to both. Their product is the HCF.

**algebra**

I don't see an inequality either. But, since the cost is not zero, you know that profit < earnings

**MAth**

If x is the middle integer, (x+4)/(x-4) = 2

**Calc**

yes. The f"' nonzero makes sure that it's not just a cup like x^4.

**Calc**

the slope has a minimum at x=c. f"(c)=0 means it's an inflection point. Think of the graph f(x) = x^3

**Math**

suppose k" = -5 on [-3,0]. You know that k'(-2) = -4. So, k'(0) would be -4+2(-5) = -14 Now, suppose that k" = -2 on [-3,0]. k' would be -4+2(-2) = -8 So, -14 <= k'(0) <= -8 remember that k" is just the slope of k'. k'(0) will lie ...

**Math**

you have ?y ? k'(-2)*?x You have k(-2), so use ?x=0.6 If the curve is concave down, it lies below the tangent line.

**Math**

6x10^-5 * 700 = (6*7)x10^(-5+2) = 42x10^-3 4x10^5 * 1.5x10^7 = (4*1.5)x10^(5+7) = 6x10^12 Now just divide as usual

**math**

just solve the system a(r^5-1)/(r-1) = 61 ar^4 = 81 Hint: 81 = 3^4

**math**

draw a diagram. Using similar triangles, h/(9+6) = 5/6

**MATH**

there are 20 students. So, the chance of getting the two freshmen is 2/20 * 1/19 = 1/190 This just selection without replacement.

**Precalculus**

the only constant I see is -1/5 I guess that make the power clear, eh?

**proofread**

I'll let bob handle the physics. You need to proofread your post this time -- get rid of the sloppy typos and finish the question.

**science URGENT!!**

hello. amplitude is wave height...

**science URGENT!!**

wave height is amplitude. and it still does not affect the frequency or the speed!

**Science**

F = ma, so a = -144/15 = -9.6 m/s^2 75 mi/hr = 33.53 m/s v = Vo + at = 33.53 - 9.6t v=0 at t=3.49 So, it will take 1.6 + 3.49 = 5.09 seconds to stop No deceleration occurs during the first 1.6 seconds, so the distance is s = 33.53*5.09 - 4.9*3.49^2 = 110.99 m

**Science. HELP!!**

not at all. The speed of light does not change because of the color. The speed of sound does not change because the pitch changes.

**Math**

The first step is to remove the parentheses. Then what do you have?

**SCIENCE**

The key to this is to come up with the equation of motion. If you review the relevant section, you will easily see that h(t) = 70+40t-4.9t^2 v(t) = 40-9.8t Now just apply your skills from Algebra I to find the vertex and find h(t)=70 and v(10)

**Math1**

just as the last one, 50=7*7+1

**Math1**

yep, it's a trinomial. If you want to factor it, recall that 15 = 2*7+1

**math**

without parentheses, exponents are done first. Remember PEMDAS? Parentheses, exponents, mult/div, add/sub So, -4^2 is evaluated as -(4^2) If you want +16, then that is (-4)^2

**math**

8×5-(6+12)÷6 = 37 as for simplifying, it doesn't get much simpler than 37 ...

**Science, Physics**

sinx(cosx-sinx) ---------------------------------- sinx(cosx+sinx)(cosx-sinx)

**Science, Physics**

sinx(cosx-sinx) ----------------------------- sinx(cosx+sinx)(cosx-sinx)

**Science, Physics**

(e2x)1/x < (x+ex+e2x)1/x < (2e2x)1/x e2 < (x+ex+e2x)1/x < 21/xe2 Now take the limits, and since 21/x-> 1, e2 < (x+ex+e2x)1/x < e2 so (x+ex+e2x)1/x = e2

**Science, Physics**

(e2x)1/x < (x+ex+e2x)1/x < (2e2x)1/x e2 < (x+ex+e2x)1/x < 21/xe2

**Science, Physics**

(e2x)1/x < (x+ex+e2x)1/x < (2e2x)1/x e(2 < (x+ex+e2x)1/x < 21/xe21/x

**Science, Physics**

(e2x)1/x < (x+ex+e2x)1/x < (2e2x)1/x

**math**

no idea. how much area does a gallon cover?

**Math**

start by expressing each factor in scientific notation: 1.31x10^5 3x10^-4 Now just multiply as usual.

**math**

the whole pipe is the sum of its parts, right?

**Math**

Since you have two values for y, just set them equal to each other: x^2+2x = 3x+20 x^2-x-20 = 0 (x-5)(x+4) = 0 and you're home free...

**College Algebra**

Once you get to 5=5 you are done. There are infinitely many solutions. If you put the two equations to the same format, they are y = 5x-5 y = 5x-5 They are the same line. Any solution to one of them is also a solution to the other.

**Math**

a+12d = 27 a+6d = 3(a+d) Now just solve for a and d.

**Math**

I agree

**Maths**

you need to learn to use parentheses online to make it clear what you want, since otherwise, multiplication gets done before addition. You meant (cot^2(x)(sec(x)-1))/(1+sin(x))=(sec^2(1-sin(x))/(1+sec(x)) Apply some of your elementary identities: cot^2(sec-1) = (sec-1)/tan^2...

**Maths**

recall that (a^3-b^3) = (a-b)(a^2+ab+b^2) sin^2+cos^2 = 1 and it all drops right out.

**chemistry**

for the same reason that any other endothermic reaction is so considered...

**Calculus**

there are lots of online graphers. You already know what the graph looks like. The critical points are where secx=0 or tanx = 0 The concavity up or down is provided by the sign of y"...

**MAth**

so, just plug in the numbers, and you should get 129

**College Algebra**

no, it is actually .05x + .10y + .25z = 7.80 Now solve 'em!

**maths steve reiny bob reiny!!! Help**

One side is the distance from (3,4) to 2x+y+3=0 The other side is the distance from (3,4) to x-2y-1=0 The area of the rectangle is thus |2*3+1*4+3)/?(2^2+1^2) * |1*3-2*4-1|/?(1^2+2^2) = 13

**Calculus**

more like dy/(1+y) = x dx ln(1+y) = x^2/2 1+y = c e^(x^2/2) y = c e^(x^2/2) - 1

**Physics**

ever hear of google? http://www.physicsclassroom.com/class/1DKin/Lesson-1/Distance-and-Displacement

**Pre calc**

so, why don't you show us how you got it? I get in QIII tan? = sin?/cos? = 5/12, so sin? = -5/13 cos? = -12/13 in QIV sin? = -1/?10 cos? = 3/?10 You don't say what you want to do with that, but sin(???) = (-5/13)(3/?10)-(-12/13)(-1/?10) = 21/(13?10)

**Calculus**

See your other post.

**Math**

a nominal rate of r compounded n times per year is (1+ r/n)^(nt) So, since you have a 4t there, .01 = r/4, making r=4% (1 + .04/4)^(4t)

**Math**

3.3*0.006*10 = 0.198 12*0.005*200 = 12 .198/12 = 0.0165 = 1.65x10^-2

**Math**

ok, so we have a circle and a tangent. A tangent to the circle will always be perpendicular to a line through the center. Now what? Ever hear of a space bar?

**Math**

(3.25*8)x10^(-22+3) = 26x10^-19 = 2.6x10^-18

**pre calc**

what are all those sin() stuff still hanging around? The final expression should just be a bunch of fractions. tan(? + ?); cos(?) = ? 1/3 ? in Quadrant III, sin(?) = 1/4 ? in Quadrant II You really need to review the signs of the trig functions in the various quadrants. In ...

**pre calc**

me either. why don't you show your work? I've done several already; your turn. I'm sure we can pinpoint where you go astray.

**Pre calc**

Funny - you and Ruth need to compare notes ... in QI sin? = 5/13 cos? = 12/13 in QII sin? = 1/?5 cos? = -2/?5 sin(?+?) = (5/13)(-2/?5)+(12/13)(1/?5) = 2/(13?5)

**Pre calc**

Better check my math, then. Also, maybe they don't want the radical in the denominator.

**Pre calc**

in QIII sin? = -5/13 cos? = -12/13 in QIV sin? = -1/?10 cos? = 3/?10 sin(? ? ?) = (-5/13)(3/?10)-(-12/13)(3/?10) = 21/(13?10)

**Math - Calc**

You forgot the chain rule. The result is (x^2)^(x^2) * 2x if f(x)=?[1,u] t^t dt and u = u(x) then f'(x) = f(u) * du/dx

**Math**

well, 141 is 11/12 std above the mean...

**Calculus - Definite Integrals Please Help!**

If you want h'(x), then that would be [cos(sin^3(x))+sin(x)]*cos(x)

**Math - Calculus**

((3x+2)/(3x-5))*3 - ((6x+2)/(6x-5))*6

**statiictis**

So, you want 4 of each kind. Pick any set of 4 from each kind, and then there will be 12! ways to play them. 21C4 * 13C4 * 25C4 * 12! = 2.593*10^19

**Calculus**

((1/2)x^2-1)^8

**math**

It's easier if you rewrite it as u = 1/x^4 u^2-u+1 = u^2-u+1/4 + 3/4 = (u - 1/2)^2 + 3/4 = (1/x^4 - 1/2)^2 + 3/4

**Math**

If all the angles are in QI, then sinA = 4/5 cosA = 3/5 sinB = 12/13 cosB = 5/13 now just use the difference formula

**Science! NEED HELP URGENT**

none. wavelength and velocity are related, but not amplitude. Now, if you're talking about something like a water wave, where water molecules are moving up and down, then of course, amplitude is related to the velocity of the moving particles.

**Geometry**

102lb * 0.45kg/lb * 2.5mg/kg = 114.75 mg

**English**

I think google is very helpful for these idioms. You can get various definitions and explanations.

**Math**

Maybe if you explain what you mean by a road a pound we can work it out. However, the perimeter of the drawing is 16 inches, and 16*5 = 80 so ...

**Language Arts**

ever see a cold, dreary, misty winter day? (between dawn and dusk, both the boundaries of the dark of night)

**trigonomenty**

Try this. http://www.cut-the-knot.org/pythagoras/cos36.shtml

**math**

plug in 3 for p: 3 = 14-2q

**Math**

distance = speed * time so just crank it out

**Math**

well, what numbers multiply to 40? example: 8*5 = 40 so, -8*5 = -40 8 * -5 = -40 Now, pick any other factors of 40. As long as an odd number of them are negative, the result is -40 2(-2)(-2)(-5) = -40 -10 * 4 = -40 and so on. Not as hard as it looked, was it?

**math**

both numbers are close to 2. What's 2+2 ?

**Maths**

well, he spent 1/4 + 1/3 = 7/12 so, what's left?

**College Algebra**

correct. Now it's smooth sailing.

**Precalculus**

so, you couldn't fix it and finish it off? The method was right in front of you ... r = 8sin? - 2cos? r^2 = 8r sin? - 2r cos? x^2+y^2 = 8y-2x That's ok as an equation, but I suspect you want a more standard form, so keep working it, completing the squares: x^2+2x + y^2...

**Precalculus**

x^2+y^2-6y-8 = 0 r^2 - 6rsin? - 8 = 0

**Precalculus**

I suspect a typo, but r = 8sin? - 2sin? r = 6sin? r sin? = 6sin^2? y = 6(x^2+y^2)

**math**

8/2 (2a+7d) = 50 50/2 (2a+49d) = 880 Solve for a and d, and then evaluate a+42d

**science**

decrease in distance, since F depends on 1/r^2

**math**

Since the terms of a GP have a common ratio r, (n+2)/(n-4) = (3n+1)/(n+2) If you solve for n, you will get two possible values. Use those to determine the appropriate values of r.

**College Algebra**

If you want to use elimination, arrange the equations so that x,y,z occur in order, and enter the coefficients into the array here: http://www.gregthatcher.com/Mathematics/GaussJordan.aspx

**College Algebra**

This one is easier to solve just using substitution: y=3z, so x+3z+z = 50 4.50x + 3(3z) + 4z = 4.38*50 Simplify those to get x + 4z = 50 4.50x + 13z = 219 Now, since x = 50-4z, 4.50(50-4z)+13z = 219 225-18z+13z = 219 5z = 6 z = 1.2 y=3z = 3.6 x=50-4z = 45.2 This makes sense, ...

**College Algebra**

you don't seem to be reading what is given. If you set up your x,y,z as you did, then x+y+z = 50 y = 3z 4.50x + 3y + 4z = 4.38*50

**College Algebra**

almost x + y = 5000 3x +7y = 23000

**College Algebra**

so, x+y=5000

**College Algebra**

No, 3x+7y = 2300 represents the total money collected. That equation is correct. How many tickets were sold?

**College Algebra**

Nope. x+y represents the total number of tickets sold. That is not 23000.

**College Algebra**

yes

**College Algebra**

You have tried to use the model where they give you the total interest earned. This one does not do that. Instead, if you read what was written, your second equation must be .08y = 32 + 2*.06x

**Maths**

hint: If 3|n^2 then 3|n*n

**Algebra**

Huh? -16*3^2+60*3+6 = 42

**Math**

the vertical mast makes a right angle with the level ground, right?