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Misturi

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Well, the bored of studies is really an online study group - we ask each other questions and others help us answer them :)

Nice suggestion though!
 

lilmzqt

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Modern Hot Chic said:
Is anyone interested in forming an on line study group to help each other out with this subject? As you know, the HSC is looming, and I thought we could all help each other out.
im all up for it! lets go!!! :D
 

Happeninchick

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lilmzqt said:
an easy way of understanding shperical geometry?? if thats possible...just CANNOT make sense of it.... :mad:

Is there anything you specifically don't understand about it, or is it just the whole concept of spherical geometry? I kind of understand the topic by mainly remembering all of the formulas.

If you aren't understanding the DISTANCE section, try to remember the formulas for converting. Heres a basic question.


Question:
Place A is situated at (25*S 20*E) and Place B is situated at (25*S 45*W). Find the distance between each place in nautical miles?

Solution:

The distance between each place is 20*+45* (Going from the West to the East because the difference is in the latitude, not the longitude) = 65*

The formula for converting degrees to Nautical Miles is 1* = 60M (nautical miles)
Therefore 65* (difference in latitude) x 60M = 3900 M

If the question then asked you to find the km, just mutliply it by the number 1.852. (Remember that number!) This number converts it to KM.

Hope that maybe helped in regards to distance!
 

lilmzqt

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its basically the whole concept.....it just confuses me and its the only part i reeli dont get....i just dun know wat to do wen....do i subtract or add here...how do i do all those time questions too? i usually get them after 3 tries and with checkin the answer but that dun help coz i cnt work from the answer in the HSC unfortunatley...
 

Happeninchick

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There is 180* from the Meridian to the East and there is also 180* from the Meridian to the West. However from the Equator to the North there is only 90* and same toward the south.

When you need to find the difference of any 2 places, if they are in the same region like for example (20*N, 30*W) and (20*N, 10*W) see how the two co-ordinates are based in the Western region - you must subtract in order to find the difference, which is 20*. Same with if you have an example like (50*N, 40*E) and (80*N, 40*E). See how the 2 are located in the northern hemisphere of the world and in the Eastern region. Therefore you must subract the 2 different co-ordinates (80 - 50 = 30*).

If the co-ordiantes are in different regions, then you must add, because you are crossing the middle line - be it the Equator (for North to South) or the Meridian (for West to East). So For example - (35*S, 40*W) and (35*S 120*E). You have a combination of SW and SE which are two differing regions. Therefore add them! 40 + 120 = 160* difference.

Now time...

Just remember: 1* = 4 minutes and East is ahead of time.

So for example, the last example I gave you...

Its 7am in Place A (35*S, 40*W). What time is it in Place B (35*S 120*E).
We worked out the difference being 40 + 120 = 160*
160* x 4mins = 640 mins
But you must now turn it in Hours to find a time so divide by 60 mins....
= 10.666666667 hours (press the degrees button to find the actual minutes instead of a decimal).
= 10 Hours and 40 mins

Now... because place A is western based and place B is Eastern based, Place B will be ahead of time in comparison to Place A.

So add 10 hours and 40 mins on 7am...
=5:40pm in Place B
 

lilmzqt

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thanx for the help! it makes much more sense now! :) 1 other thing tho. what if all the numbers are different. eg. i dunno.....(40*N, 125*W) and (63*N, 47*W)
or there are'nt common regions eg. (40*N, 125*W) and (63*S, 125*E) then wat do i do there?
 

Happeninchick

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I so knew you were going to ask me that question! LOL I have been wondering about it myself. I've looked over all my notes and text books! The only questions for distance or time, seem to only relate to co-ordinates that always have one remaining the same. For example (40*N, 125*W) and (63*N, 125*W) - The West being the same. I've been through them all and they all seem to have a common region along with a common co-ordinate.

If anyone has got an example of how to find distance and time with all different regions or co-ordinates - it would be great if you could post them up, as I can't seem to find any. I really don't think it is possible to find it without some formula (that we obviously haven't learnt).

Do you understand all about speed? Like about knots? And Nautical miles?

Just remember that:
1' min = 1 M (nautical mile)
Therefore 60 mins makes up 1*
1* = 60 M

1 M also = 1 kn (knot)

There just seems to be so much converting in it all... ARGH! Hehe

Just a few questions that might help. See if you can work them out.

Q1
Find the distance in km between (75*S, 123*W) and (75*S, 25*E).

Q2
Find the distance from (27*S, 100*E) to (34*N, 100*E).

Q3
It takes a boat 18 hours to travel from (47*N, 66*E) to (32*N, 66*E). What is its average speed in knots?
 
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Q

Study the extract from the credit card statement below.
Interest Rate = 19.5% p.a Daily rate = ?

Date Credit ($) Debit ($) Balance ($)
1 Jan. 2584.75
6 Jan. 600 - repayment
15 Jan. 39.99 - purchase
1 Feb ??? - Interest
8 Feb ???? - repayment
15 Feb 425.85 - purchase
1 March ??? -interest

a. Calculate the daily rate of interese (take 1 year = 365.25 days and answer correct to 4 decimal places).
b. Calculate the interest due for January.
c. If the minimum monthly repayment of 5 % of the outstanding balance is made on 8 February, calculate the amount of this repayment.
d. Calculate the interest for February.

Please help - I don't understand it.
 

lil_lainy

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hello fellow peeps...just a quick question about spherical geometry/ time differences...i know how to work out the time difference between 2 plcs, but i dont know which place should be ahead and which should be behind, if that makes any sense, unless i have a map ofthe world in front of me

so yeh i was just wondering if anyone could help me with this
 

lil_lainy

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hmmm...

so if one plc (A) is 75`W..the otha (B) is 15`E

time dif is 6 hrs

if it is 1.00pm at A, do i add 6 hrs or subtract to get time at B
 

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