IGCSE MATHS Doubts

[PeaceMaker]

they arent wrong, the ms cant be wrong, which paper is this q from??

If your talking to me, i said that i asked the wrong Paper i wrote 2003 when i really wanted the answers of those questions from paper 2005

[Vin]

I know you got this already, but i don't mind elaborating  

        90  
     S  |  A
180----------0/360
     T  |  C  
       270
Read the above as follows before starting:
1) A=All +ve , S= Sin +ve , T=Tan +ve , C=Cos +ve
2) This shows the four quadrants, going anticlockwise from 0 to 90 to 180 270 to 360.
3) This means that any angle in a specific quadrant is +ve acc to 1)
So, now coming to your question, the question is talking about sin, which is +ve in the 1st and 2nd quadrant.
The angle already given to us is in the 1st quadrant, so now we know we will get the same value in the second quadrant in the 2nd quadrant (180-x) or the after 360 (360+x)
Taking -50 to be x
we have the other two angles as,
180-(-50) = 180+50 = 230
360+(-50) = 360-50 = 310
hope that helps, not specifically for this question, but in general.

Ohh cool !! hadta read it thrice tho but i get it.. Thanks ..

[Fastal]

can we look at my questions now
i made it easier by doing the previous bits---see attached pictures
img010 is for 2(d)(iii) from 2005 november p4
3(a)(iv) is from 2005 june p4

[Ghost Of Highbury]

I know you got this already, but i don't mind elaborating  

        90  
     S  |  A
180----------0/360
     T  |  C  
       270
Read the above as follows before starting:
1) A=All +ve , S= Sin +ve , T=Tan +ve , C=Cos +ve
2) This shows the four quadrants, going anticlockwise from 0 to 90 to 180 270 to 360.
3) This means that any angle in a specific quadrant is +ve acc to 1)
So, now coming to your question, the question is talking about sin, which is +ve in the 1st and 2nd quadrant.
The angle already given to us is in the 1st quadrant, so now we know we will get the same value in the second quadrant in the 2nd quadrant (180-x) or the after 360 (360+x)
Taking -50 to be x
we have the other two angles as,
180-(-50) = 180+50 = 230
360+(-50) = 360-50 = 310
hope that helps, not specifically for this question, but in general.

lol, gr8 u did, i was pretty bored to type it..By the way

just to add something here..v had a mnemonic to remember the All Sine tan cos.

its All silver tea cups.

all , sine cos tan.

[Ghost Of Highbury]

can we look at my questions now
i made it easier by doing the previous bits---see attached pictures
img010 is for 2(d)(iii) from 2005 november p4
3(a)(iv) is from 2005 june p4

sorry for the late reply.

heres 2)d)iii

work out the inverse first.

determinant - 1.5

(1/1.5     0   ) = (2/3  0)
(  0    1.5/1.5)   (0     1)

now first, u have to learn this list of matrix transformations, dont learn them all, learn the imp. ones like shear , stretch, enlargement etc, heres it : https://studentforums.biz/index.php/topic,5575.msg167872.html#msg167872  (3rd post)

and this is what it says abt stretch

Stretch

1. x invariant  wer k=scale factor (1 0)
                                             (0 k)

2. y invariant  wer k=scale factor (k 0)
                                             (0 1)

now if u notice, out matrix is like the 2. one.

therefore, it means, that its stretch with y invariant and scale factor = k = 2/3

and abt the shear question, sry, im a little confused myself. will try to help asap/

[ksitna]

kk i know u guys are gonna kill me but
well i dont get this question either

A cylindrical glass has a radius of 3 centimetres and a height of 7 centimetres.
A large cylindrical jar full of water is a similar shape to the glass.
The glass can be filled with water from the jar exactly 216 times.
Work out the radius and height of the jar.

[Ghost Of Highbury]

Volume of glass = Pi*r²*h = 63Pi

so volume of jar = 216* 63Pi = 13608Pi cm³

since jar is similar shape to glass then ratio of height / radius of the jar = 7/3

let height of jar = h cm

h/r = 7/3

r/h = 3/7

r = 3h/7

volume of jar = Pi *(3h/7)²*h
= 9h²/49 * h * Pi
= ( 9/49)*h³* Pi

so (9/49)*h³* Pi = 13608Pi
h^3 = 13608*(49/ 9)

h = 42 => r = 42 * 3/7 = 18

r = 18 cm and h = 42 cm

[ksitna]

thank youuuu

[idrees]

um i asked this Q .. really no one helped
can someone please explain the question

june 2007 p4 q7

hey i really need help with this Q.

its killing me! if someone could just explain the dynamics of this q .. how do i go about solving the question. thats all i need .. im really good at mensuration, i have just forgotten how to solve questions regarding rate of flow of water ..

June 2007 p4 Q7

Thanks a LOT!

[Vin]

um i asked this Q .. really no one helped
can someone please explain the question

june 2007 p4 q7

sure .. gimme some time ..

[Dibss]

well i dont get this question either

A cylindrical glass has a radius of 3 centimetres and a height of 7 centimetres.
A large cylindrical jar full of water is a similar shape to the glass.
The glass can be filled with water from the jar exactly 216 times.
Work out the radius and height of the jar.

Volume of glass = Pi*r2*h = 63Pi

so volume of jar = 216* 63Pi = 13608Pi cm3

since jar is similar shape to glass then ratio of height / radius of the jar = 7/3

let height of jar = h cm

h/r = 7/3

r/h = 3/7

r = 3h/7

volume of jar = Pi *(3h/7)2*h
= 9h2/49 * h * Pi
= ( 9/49)*h3* Pi

so (9/49)*h3* Pi = 13608Pi
h^3 = 13608*(49/ 9)

h = 42 => r = 42 * 3/7 = 18

r = 18 cm and h = 42 cm

there's a simpler way if you'd like actually...
(ratio of lengths)^3 = ratio of volumes
ratio of volumes = 1:216 and if you find the cube root you get ratio of sides as 1:6
then you simply multiply each length by 3 and get
r= 3x6 = 18cm
h= 7x6 = 42cm
make sense?

[Dibss]

then you simply multiply each length

sorry, typo... meant 6

[Vin]

um i asked this Q .. really no one helped
can someone please explain the question

june 2007 p4 q7

Got it !! quite easy ..
 a) is quite direct ..
for such kinda ques wat i always do is look for the units .. for eq in this one..
they hav asked Calculate the number of cubic metres .. 3 measurements hav to be multiplied (this is jus a tip .. this is how i under the ques)

so for this vol = 0.3 m  x  1.2  x 3 m/min x 60 (for 1 hour)

= 64.8 cm³
-----------------------------------
b) same method as the previous ..
first
vol =  0.8m  x  1.2m  x  15 m/min  x  60
= 864 cm³

for % , difference is 864 - 64.8 = 799.2
per cent = diff/original  x 100
= 799.2
 ---------  x  100
   64.8
= 1230 %

-----------------------------------
c) firstly always remember to convert ur units to units asked in ques..
1.3 mm = 0.0013m

vol  =  pi r^rh
2   =  pi r² x 0.0013
on solvin = 22.1 m

-----------------------------------
d)  take the length as L ..

surface area =  50.4/0.12
= 420 m²

SA = (0.8 x L) +  (1.2 x L) + (0.8 x L)
420 = 0.8L + 1.2L + 0.8L
420 = 2.8 L
L = 150m .. done !!
 

[$H00t!N& $t@r]

Hey guys do you have any notes on sine and cosine curve? If not then do you know any good site on that.
Thanks in advance!

[Dibss]

do you need this for math or add math since i can't seem to remember any sine/cosine curve qs in math past papers...
do you mean sine/cosine rules by any chance?