trap (1 Viewer)

[crammy90]

Using trapezoidal rule 4 function values estimate volume of area between x axis and y=4-(4/x)
i get down to there answer (pi/2)[0+2(4+7r1/9)+9]
but then the answers get 35.1 ldp
i get 49.0 1dp:S

for this when finding the area of shaded, how come we dont have to split the integral if they are two curves overlapping :S

 

[dolbinau]

For your first question, I get 49.04375 by just putting that in the calculator. You probably need to work with brackets or something.

For the second, this is something I have an issue with - but the best way I understand it, is, if you move both of the curves up the y axes it doesn't matter where they are, the area between the curves is always the same.

However, if you moved a curve that had area under it bound by the axes and moved it up the area would change.

At least this is how my teacher described it

http://img80.imageshack.us/my.php?image=picture5zz6.png

See how the area will change? but that curve won't if it moves? I don't know if this is a right way to describe, but it works for me!

 

[crammy90]

ok thanks heaps
that makes sense

yeh i dno with the brackets thing :S

 

[dolbinau]

In the calculator

4+7r1r9 then press EQUALS then times two then plus nine then press EQUALS then times by pi/2

Or try and enter it with the brackets exactly as it is

 

[Just.Snaz]

IT'S A TRAPPPPP!

couldn't resist

 

[crammy90]

In the calculator

4+7r1r9 then press EQUALS then times two then plus nine then press EQUALS then times by pi/2

Or try and enter it with the brackets exactly as it is

i did that and got 49 again lol
there answer was the 35.1
ill re-edit the wording

with this the sides AC and CB are a road. AC is constructed accross water and costs 5 times more to construct than it does to construct CB which is on land. K is the cost of constructing 1km of road on land. We are asked to find an expression in terms of theta for the cost. The diagram above is the 1 we are given.

this is the one in the answers (notice they added the sin and tan parts)
WORKING:
AC = sin(theta)
BC = 2-tan(theta)
Cost = 5ksin(theta) + k(2-tantheta)
i get that sine(theta) is opposite/hypotenuse and that stuff. But how do you know what side the sine goes on. hard to explain: ill elaborate:
sin = opp/hyp
sin = C-->right angle/AC
they put the sine on the hyp AC but not the C-->rightangle
Furthermore:
Tan = opp/adj
= C-->right angle/1
they put the tan theta on the c-->right angle but not the 1
i hope ppl can understand that lol

 

[dolbinau]

ohh You get 49 too. I thought you meant THEY get the 35. Yeah I think there must be a mistake in the working. (Can't be bothered to go through that working though, English!) But yeah. I think they got it wrong then.

 

[minijumbuk]

y=cos2x graph looks wrong.