Mathematics: Post your doubts here!

[Rutzaba]

daredevil syed1995 @mostafamotani asd Rutzaba part (ii) ASAP

do u have the answer to this
sumhow my values are coming in decimals

 

[daredevil]

Well, I also tried CA x CB and get the correct answer, I just don´t get why using AC x AB or CA x BA I get the wrong answer.

i tried it out too and God u're ryt... it doesnt make sense! >__<

 

[Namehere]

i tried it out too and God u're ryt... it doesnt make sense! >__<

Good! I´m not alone anymore!

Someone shine some light on us please!

 

[Rutzaba]

A star
last line nhi horhi thi to internet se uthaya hai ye solution baki hogya tha...

 

[Rutzaba]

View attachment 41146 View attachment 41145

Rutzaba
Please help..

m1?

 

[Rutzaba]

View attachment 41146 View attachment 41145

Rutzaba
Please help..

i can only tell part b

 

[Rutzaba]

View attachment 41146 View attachment 41145

Rutzaba
Please help..

since its gp u can say that the common ratio r is k
and the first term theta as we are dealing in angles...
the first term a =Q
so we have
ar ,a r^2, ar^3...
Qk,Qk^2,Qk^3...
you know that the sum to all angles in a circle is 360 or 2pi
and the sum to infinity is = a/1-r
Q/1-k = 2pi
Q=2pi(1-k)

 

[Rutzaba]

dw.. I got part A
View attachment 41151

it can be done in both ways

 

[Ahmed H. Al-Neel]

help with s12 paper 12 question 7a please!!
http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_s12_qp_12.pdf

 

[Rutzaba]

And the first one??

i told u i dunno how to do it...

 

[daredevil]

A star
last line nhi horhi thi to internet se uthaya hai ye solution baki hogya tha...

can u explain part ii plzz??? :`)

 

[Talha Khatri]

Good! I´m not alone anymore!

Someone shine some light on us please!

Guys, just remember, you should always, always find the cross product this way: AB x BC always from one point to another and then from the same common point to the next. Just stick to one thing and don't confuse yourself too much

 

[Rutzaba]

can u explain part ii plzz??? :`)

the first thingit says is that on q lies theline AB
that means a straight line on ab wud be perpendicular to its normal vector...
that means the directional vector of line= b1 wud be perp to norm vector of plane
so dot product of b1(OB-OA) =(3,1,-1) . (1,b, c) (coeff of x y and z in the plane) = 0
from here we get b=c-3
get this much/
consider this eq 1
then we know the angle between two planes= n1.n2=|n1||n2|cos theta
here they gave us theta to be 60degrees
note that the plane give has norm vector (coeff of eq of plane 1)
(1,1,0)
and (1, b, c)
|n1|= root 2
|n2|= root 1+b^2 +c^2
(1,1,0).(1, b, c)= root 2 * root 1+b^2 +c^2 * -0.5(since acute =60 obtuse 120)
-2(1+b)=root 2 +2^2 +2c^2
substitute the value of c=b-3 into this eq and wala

 

[A star]

A star
last line nhi horhi thi to internet se uthaya hai ye solution baki hogya tha...

repeat it please cant get how you found out two normals

 

[A star]

the first thingit says is that on q lies theline AB
that means a straight line on ab wud be perpendicular to its normal vector...
that means the directional vector of line= b1 wud be perp to norm vector of plane
so dot product of b1(OB-OA) =(3,1,-1) . (1,b, c) (coeff of x y and z in the plane) = 0
from here we get b=c-3
get this much/

in englis pls :3

 

[Serenia]

Hello!

I have a doubt in question 8(ii) on this P1 exam.
I could find the value of r when A has a stationary value, but I can't show that there are no straight sections in the track. I looked at the mark scheme but I don't understand that part. The second part (determine the nature of the stationary point) I can do.

Attached I am sending the paper and the mark scheme.

Thanks in advance.

 

[Rutzaba]

repeat it please cant get how you found out two normals

the coefficient of x y and z

 

[Namehere]

Guys, just remember, you should always, always find the cross product this way: AB x BC always from one point to another and then from the same common point to the next. Just stick to one thing and don't confuse yourself too much

Well, as i mentioned before, I also did it with CA x CB (and many other combinations) and got it right, so your theory fall to pieces there ^^ I just don´t get why using AC x AB or CA x BA I get the wrong answer!

 

[midha.ch]

Can anyone solve the first question in the attached file. It's the one related to cards. help needed asap please

 

[Talha Khatri]

Well, as i mentioned before, I also did it with CA x CB (and many other combinations) and got it right, so your theory fall to pieces there ^^ I just don´t get why using AC x AB or CA x BA I get the wrong answer!

No, you did not understand what I told you. I said, just stick to one thing. I don't know how many more ways there are to get the right answer but remembering this method is easy and it is consistent, you always get the right answer so I would recommend you to stick to just one method instead of confusing your self