# Posts by Steve

Total # Posts: 51,159

**Math (Integrals) (Using given method)**

yes. so you have 1/2 ?sin2x dx let u = 2x, du=2dx and you have 1/4 ?sinu du = -1/4 cosu = -1/4 cos(2x) + C

**calculus**

?[0,4] ?(1+y'^2) dx = ?[0,4] ?(1+(12x^2+3)^2) dx

**math**

two bases 10*3 two sides 12*10 two sides 12*6

**math**

you can play around here, and see how things work: http://www.wolframalpha.com/input/?i=plot+3%2F7+x+%2B+6,+3%2F7x-3

**Calculus**

3.18-? = 0.0384 0.0384/? = .0122 = 1.22%

**Algebra**

B+A

**Science**

see related questions below

**trigonometry**

using the quadratic formula, sin(x) = 3/4 (1±?5) = -2.4 or 0.927 Now just find the two values of x which make that work.

**math**

42

**Math**

area of triangle base: 0.5*3.1*3.5 = 5.4 cm^2 volume = 5.4*21 area = 3*21*3.5 + 2*5.4

**hello jishka maths tutor please help me**

This appears to involve Airy functions, which are not your usual elementary functions. See http://mathworld.wolfram.com/AiryFunctions.html

**Physics**

I suspect a typo. No way is a wire going to increase in length by a factor of 10. Also, your coefficient is lacking some units. In any case, if it grows by 16.66*10^-6 cm for each °C, just divide the length increase by that number.

**math**

Let's say the initial rate is 6% In that case, the value after 44 years will be [4000(1+.06/2)^(2*22)](1+.0628/4)^(4*22) = 57,843.92 If the initial rate is not 6%, just change it in the expression above and re-evaluate.

**Calculus**

well, just plug in x=4! (f(4)-5)/(4-2) = 1 f(4)-5 = 2 f(4) = 7 In the absence of anything to indicate that f(x) is not continuous, I assume that lim(x->4) f(x) = f(4)

**maths steve plz steve reiny help am dieing**

That's "dying" and I have no ideas what your three angles are supposed to be. If they are the angles of a triangle, just draw a line at one vertex, parallel to the opposite base. Next, recall that alternate interior angles between parallel lines are congruent. ...

**Pre algebra**

C = 6P

**word problem**

x+y = 12 2x+3y = 29

**geometry**

the slant height of the pyramid is the altitude of each triangular face. Now you have four triangles, and you know their base and height. I assume you can take it from here.

**Math**

compare 6/9 to tan35°

**Math**

4/x = 0.25

**math**

as written, it is linear. But it is an odd way to write it. If you meant 2•3n-1 it is exponential

**Math**

If you take all the numbers from 1 to 30, there are 15 multiples of 2 7 multiples of 2^2=4 3 multiples of 2^3=8 1 multiple of 2^4=16 So, 2 occurs 15+7+3+1 = 26 times N = 26

**Math (Check Answer)**

Not so. Just expand the expression 5+2(r+7) = 5+2r+14 = 2r+16 2+5(r+7) = 2+5r+35 = 5r+35 Try that with the other pairs, and see which comes out with both sides the same.

**math**

240/1.2c = 240/c - 4

**Math**

you are correct that there are 4 lights. But that means one at each end, and two in the middle. There are only three spaces between lights, of 2m each. It's always better to draw a diagram, and this would have been clear.

**algebra**

5/7 x = 15000 x = 21000

**maths**

there are only 5 even digits. So, if each us used at most twice, that makes a total of at most ten digits used. Looks like your sequence can consist of only two 5-digit numbers. One such pair is 22446 68800

**Math**

kinda vague, eh?

**math**

s = r? You have s and ? (hint: a full circle is 2?), so find r. a = 1/2 r^2 ? then let 'er rip and that's pi, not pie!

**calculus**

The region of interest is just a small patch above the x-axis. y ranges from 0 to 1, but the right boundary changes at 1/?2. The volume consists of a cylindrical ring of thickness 1/?2 plus a shape with curved edge. using shells of thickness dy v = ?2?rh dy where r=y+1 and h=x...

**maths**

If he started with x, then (x-4)/2 = 30

**maths**

m/j = 5/7 j = m+18 solve for m and j. Then you want (m+9)/(j-9)

**calculus**

exploiting symmetry, we can say a = 2?[0,?/2] 1/2 r^2 d? = ?[0,?/2] sin2? d? = 1

**calculus**

y = r sin? x = r cos? dy = sin? dr + r cos? d? dx = cos? dr - r sin? d? so, the slope of the tangent line is dy/dx = (sin? dr + r cos? d?)/(cos? dr - r sin? d?) at ?=?, dy/dx = r d?/dr = r(-6/r^2) = -?^2/6 so, now we have a point and a slope, so the tangent line is y = -?^2/6...

**calculus**

r^2(cos^2?-sin^2?) = 1 r^2 cos^2? - r^2 sin^2? = 1 x^2-y^2 = 1

**calculus**

?[0,1] 2?x ds = ?[0,1] 2?x?(x'^2 + y'^2) dt = ?[0,1] 2?t^3?((3t^2)^2 + (2t)^2) dt Not an easy one -- it will involve integration by parts. http://www.wolframalpha.com/input/?i=%E2%88%AB%5B0,1%5D+(2%CF%80t%5E3%E2%88%9A((3t%5E2)%5E2+%2B+(2t)%5E2))+dt

**calculus**

a = ?[0,2] ?t (2t-2) dt = 8?2/15

**MATH**

it depends on what you are given. If you draw a diagram of the situation, you will find that tan? or sin? will probably give you your answer.

**Physical Science**

What will be the total resistance and current in a parallel circuit with a 15-volt battery and 3 10-ohm resistors?

**Math**

OK you started with 90 equations You didn't attempt 2 so 90-2=88 You missed 14 so 88-14=74and -14 for wrong answers You got 74 correct so 74*4= 296 and then 296-14=282 total score

**algebra**

-7?(6-5)?(54) = -7(?1)(3?6) = -21?6 I suspect a typo...

**Calculus**

Consider g(x) = f(x)-x g(0) = f(0)-0 >= 0 g(1) = f(1)-1 <= 0 since g is continuous, either g(1)=0 or g(1) < 0. If g(1) < 0, the Intermediate Value Theorem tells us that at some point c in the interval, g(x) = 0

**math**

it would be e^(sin x^2)*2x - e^(cosx) * (-sinx) This is just the chain rule via the back door. If F(t) = ?f(t) dt then ?[u,v] f(t) dt = F(v) - F(u) Now take the derivative, remembering the chain rule.

**Calculus**

#1. No consider f(x) = e^(-x^2) #2. No consider f(x) = -x^2 See what you can do with #3.

**Algebra 2 check my last answer?!**

where did you learn to write fractions? 2?/3 is the way to write it. However, your choice is not quite correct. You forgot the reflection part. So, the correct answer is f(x) = ?10cos(2?/3 x)+10 -10cos(2?/3 x) has max/min at 10,-10 and is a reflection of cos(2?/3 x) Now add 10...

**pre-calc**

S1: 2 | 1^2 + 7*1 2 | 1+7 2 | 8 true do likewise for n=2,3

**algebra**

I shall use x instead of whatever character you chose to copy/paste. The graph of y = a sin bx has amplitude = |a| period = 2?/b so, what do you get?

**Trigonometric Functions?**

quite a few maybe the easiest to use is wolframalpha.com desmos.com fooplot.com https://rechneronline.de/function-graphs/ are all good sites with lots of versatility

**statistics**

for any general question, google is always a good place to start. https://www.google.com/search?q=estimated+probability&ie=utf-8&oe=utf-8

**Math**

15/x = 3/4 If the areas are in the ratio 9:16 then the sides (which are the square root of the areas) are in the ratio ?9:?16 3:4 = 15:20

**Math**

the sides are in the ratio 3:4, so ...

**graphing help?**

wolframalpha.com is very easy to use. Just type in your function, and it will show the graph. For example, http://www.wolframalpha.com/input/?i=4sin(3t)%2B2

**Algebra 2 check**

almost. If the max is 12 and the min is -6 then the midpoint is at (12-6)/2 = 3 So, f(x)=9sin(6?x)+3 your choice has max = -6+9 = 3 min = -6-9 = -15

**C++ programming**

you really expect someone to do this whole thing for you? How about you pick some piece of it that causes trouble, and show some ideas you have so far. I'd bet that there are code samples online for just about any part of it that you can break out.

**calculus**

kind of tricky, eh? Let x = e^u. Then u = lnx du = 1/x dx, so dx = x du = e^u du Now the integral is ? sin(5lnx) dx = ? sin(5u) e^u du = ? e^u sin(5u) du and you can apply your formula.

**math**

oops. My answer was the amount earned in the 39th week. To find how much he has earned during the whole 39 weeks, use the sum formula: S39 = 39/2 (2*135 + 38*5) = 8970

**math**

135 + 38*5

**calculus**

the slope is dy/dx = (dy/dt)/(dx/dt) = (sint + tcost)/(cost - t sint) y'(?) = (0-?)/(-1-0) = ? at t=?, x=-? and y=0 so, using the point slope form of the line, y = ?(x+?)

**calculus**

clearly, x^2+y^2 = 1 The question is, how much of the circle is graphed? ? x y -? -1 0 0 0 1 ? 1 0 we only get the top half of the circle.

**Geometry**

what figure?

**Math**

5/3 as many days, so 5/3 as much pay.

**Calculus**

well, you know the slope on one side is 1.4 and the slope on the other side is -1.4 You have the point (12,1.2) so the region has two lines for its boundary: y = 1.4(x-12)+1.2 = -15.6+1.4x y = -1.4(x-12)+1.2 = 18-1.4x Type in the functions at wolframalpha.com and you can see ...

**Calculus**

Well, clearly you did not bother to evaluate the integral yourself. I made a typo, and the answer is 864?/35 instead. Just to check, we can apply the theorem of Pappus. The area of the triangular region is (1/2)(6/5)(12/7) = 36/35 The centroid is at x=12, so the distance ...

**Calculus**

v = ?2?rh dx where r=x and h=y v = ?[78/7,90/7] 2?x(6/5 - 7/5 |x-12|) dx = 8634?/35

**algebra**

too bad you don't show your work. Just doing the decimal values, I get 8.97436 I agree with your evaluation of Reiny's final line, so let's see what went wrong. Did you bother to check his math? His only mistake was to omit the leading minus sign. Had you corrected...

**Geometry**

Since LM and KN are parallel, alternate interior angles ?LKM and ?LMK are congruent. So, ?LKM is isosceles. That means that KL=LM. So, since LM:KN=8:9, we can say that LM=8x and KN=9x. That means that KL=MN=8x, and thus 8x+9x+8x+8x = 132 33x = 132 x = 4 The legs KL and MN are ...

**Math**

(4+5)/100 = 9/100

**Math**

small oops: 20/3 = 6.6

**Math**

just divide, as with any fraction. 18/5 = 3.6 20/3 = 6.3 It just means that the value left of the decimal point will be greater than 0.

**geometry**

You have not made it clear what ?1 and ?2 are. Try using letters, such as ?1 = ?KNM or something Also, which sides are the parallel bases? If they are KL and MN, then the figure is a parallelogram. Is PKLMN the perimeter? Or is P some other point outside the trapezoid. You ...

**SCIENCE CHEMISTRY**

Where does the Chlorine come in? CH3OH = 12 + 3*1 + 16 + 1 = 32

**Math help? Someone help me?**

Still no. try (A) If there is a min or max, the curve folds back on itself, so it is no longer invertible. It fails the horizontal line test.

**Math**

no, y is on a bearing of 60° from x. The man travels on a heading of 60° Draw a diagram. In ?XYZ, you have angles X = 30° Y = 45° Z = 105° so, using the law of sines, y/sin30° = 200/sin105° = z/sin105°

**Math**

#1: y = 3-2x so, 5x-(3-2x) = 11 7x = 14 x = 2 now you can find y using either equation.

**Math**

see your earlier post

**Physics**

If you draw the diagram, since 25 sin35º = 14, then the angle ? south of W is tan? = (18-14)/20 = 4/20 ? = 11.3º

**Trigonometry**

lowest height = 4 - 3 = 1 greatest height = 4 - 3/2 = 5/2 amplitude = (5/2 - 1)/2 = 3/4

**Algebra 2 check my last answer?!**

and we have a winner! B it is

**math helpppp?!**

looks good to me

**algebra 2 help asap**

just replace x with 3. Same as you have done for the last year or so in algebra... f(3) = 81 + 3e^(-0.7*3) = 81 + 3e^-.21 = 81 + .81058 = 81.81058 Better get out your calculator (physical or online) for these!

**math please help ASAP**

see your previous post. Why did you repost with the same error in typing? And are you sure this is algebra 2, and not calculus? Maxima and rates of change are usually not doable with just algebra.

**algebra 2 please help :(**

NO! x = 0.73

**algebra 2 please help :(**

Hmmm. f'(ln9/3) = 15 not 10 or 20

**algebra 2 please help :(**

some parens help make things clearer online: f(x)=20/(1+9e^(-3x)) f'(x) = 540e^(3x)/(9+e^(3x))^2 the greatest growth rate occurs when f' has a maximum. So, f"(x) = 1620e^3x * (9-e^3x)/(9+e^3x)^3 since the denominator is never zero, f" is zero when e^3x = 9 x...

**College Alebra**

x+y+z = 26 y = 3x+1 z = 5x-2 hat do you get?

**maths**

If there were originally b boys and g girls, .60b + .90g = .75(b+g) .9g = .6b+12 solve for b It's a bit less cumbersome if you get rid of those pesky decimals 60b+90g = 75b+75g 3g = 2b+40 60b + 30(2b+40) = 75b+25(2b+40) b = 40

**math help urgent please**

I disagree. If f(x) is the cost for x tickets, then each ticket costs (.50x+10)/x = .50 + 10/x and ... ?

**GEOMETRY**

if it goes on without repeating, it is irrational. If it reaches a digit of group of digits that repeat forever, it is rational.

**GEOMETRY**

and is 16.5 closer to 15.8 than 16?

**GEOMETRY**

#1 ok #2 Any decimal which repeats is rational #3 nope. ?150 = 25?2 -- irrational #6 no diagram #7 How can you possibly say that the pole is 16 times as high as the length of the cable? You are clearly just guessing here. When you get an answer, take a step back and see ...

**math**

160*0.9/6 = 24

**Algebra help?? Stuck!**

I get 6220 That 6200 is unlikely, since the first two terms don't ad to zero...

**I don't get this math!**

The sequences are 1,2,4,8,16,32,64,128,256,512,1024 1,2,4,9,16,25,36,49,64,81,100 1024/100 = 256/25 = (16/5)^2

**algebra**

a) note that you just keep subtracting 2, so an = 1+2(n-1) = 2n-1 b) Hmmm. Differences are 8, 2, 3, 9, ... .-6, 1, 6, ... ....7, 5 ... Not a quadratic. The terms are 8, 8(1/4), 2(6/4), 3(12/4), ... The numerators are 1,6,12. Again, not much good there. The sequence is very ...

**math!!**

The AP numbers are: a, a+d, a+2d The GP numbers are: b, br, br^2 Add the terms, and you get a+b = 32 a+d+br = 26 a+2d+br^2 = 32 a+a+d+a+2d = 51 Now you have 4 equations for 4 variables. Use your favorite method to solve them (I suggest substitution), and you end up with AP: 5...

**math- ouch!**

Looks like I had mismatched subscript tags. I meant #1. quadratic sequences have a constant second difference. In this case, 4. The sequence and differences are -1, 2, 9, 20, 35, ... ...3, 7, 11, 15, ... .....4, 4, 4, ... So, the 1st differences form an arithmetic progression...

**math- Please help**

#1. quadratic sequences have a constant second difference. In this case, 4. The sequence and differences are -1, 2, 9, 20, 35, ... ...3, 7, 11, 15, ... .....4, 4, 4, ... So, the 1st differences form an arithmetic progression: 3 + 4k So, a1 = -1 an+1 = an + 3+4(n-2) or, an+1 = ...

**Trig**

Draw a diagram. If the length is x, then 142.9/x = cos 32.1°

**Math**

x = Rohit's age now y = Roshni's age now x = 2y x-5 = 3(y-5) Now just solve for x and y

**Probability theory**

10*1/13 + 2*1/13 + 1*1/13 - 2 = -1 better go back to class and stop gambling