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# Very annoying c1 question Tweet

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1. Very annoying c1 question

It says in the mark scheme the coordinates for B = x, 11 - 2x

I used x,y and tried working it out that way, I don't understand where they got 11 - 2x from?

Oh actually I do get where they got it from they got it from the equation of the line, but how is that the y - coordinate?
Last edited by IShouldBeRevising_; 12-05-2012 at 17:38.
2. Re: Very annoying c1 question
(y-5) = -2(x-3)

y - 5 = 6 - 2x
y = 11 - 2x

I cannot get that you understand this is the line but do not understand that it gives you y
3. Re: Very annoying c1 question
(Original post by TenOfThem)
(y-5) = -2(x-3)

y - 5 = 6 - 2x
y = 11 - 2x

I cannot get that you understand this is the line but do not understand that it gives you y
hmm don't know never come across such a question before
4. Re: Very annoying c1 question
(Original post by IShouldBeRevising_)

It says in the mark scheme the coordinates for B = x, 11 - 2x

I used x,y and tried working it out that way, I don't understand where they got 11 - 2x from?

Oh actually I do get where they got it from they got it from the equation of the line, but how is that the y - coordinate?
The equation of the line is .

Point B lies on this line, so its coordinates are

We know the coordinates of A, so use the formula we use for finding the distance between 2 points.
5. Re: Very annoying c1 question
(Original post by raheem94)
The equation of the line is .

Point B lies on this line, so its coordinates are

We know the coordinates of A, so use the formula we use for finding the distance between 2 points.
Yeah I get the method, just didn't know why the y coordinate was 11-2x, but do now.

Btw if you have a straight line with gradient 1 the tangent to this line has gradient -1, does the gradient of the normal to the line also = -1?
6. Re: Very annoying c1 question
(Original post by IShouldBeRevising_)
Yeah I get the method, just didn't know why the y coordinate was 11-2x, but do now.

Btw if you have a straight line with gradient 1 the tangent to this line has gradient -1, does the gradient of the normal to the line also = -1?
If you have a straight line it can not have a tangent to it

If you have a curve with gradient 1 at a given point then the tangent to the curve at that point also has gradient 1

and the gradient of the normal would be -1
7. Re: Very annoying c1 question
(Original post by IShouldBeRevising_)
Yeah I get the method, just didn't know why the y coordinate was 11-2x, but do now.

Btw if you have a straight line with gradient 1 the tangent to this line has gradient -1, does the gradient of the normal to the line also = -1?
Do we ever draw tangents to straight lines?
8. Re: Very annoying c1 question
(Original post by IShouldBeRevising_)
Btw if you have a straight line with gradient 1 the tangent to this line has gradient -1, does the gradient of the normal to the line also = -1?
The gradient of the normal would be -1.

If you did figure out a tangent to a straight line it would have the same gradient as the line. However, tangent to a straight line = straight line so you'd never need to figure that out.
9. Re: Very annoying c1 question
(Original post by TenOfThem)
If you have a straight line it can not have a tangent to it

If you have a curve with gradient 1 at a given point then the tangent to the curve at that point also has gradient 1

and the gradient of the normal would be -1

(Original post by raheem94)
Do we ever draw tangents to straight lines?

(Original post by JamieEclipse)
The gradient of the normal would be -1.

If you did figure out a tangent to a straight line it would have the same gradient as the line. However, tangent to a straight line = straight line so you'd never need to figure that out.
Yeah just got confused thanks for the help, very speedy service :P
10. Re: Very annoying c1 question
(Original post by IShouldBeRevising_)
Yeah just got confused thanks for the help, very speedy service :P
Is the answer (9,-7) and (-3,17) ?
11. Re: Very annoying c1 question
(Original post by bong)
Is the answer (9,-7) and (-3,17) ?
Nope
12. Re: Very annoying c1 question
lol C1. Those were the days...
13. Re: Very annoying c1 question
(Original post by masterhr1)
lol C1. Those were the days...
lol why what you doing?
14. Re: Very annoying c1 question
What paper is this question from?
15. Re: Very annoying c1 question
(Original post by Buongiorno)
What paper is this question from?
January 2012
16. Re: Very annoying c1 question
(Original post by IShouldBeRevising_)
January 2012
Thanks. Edexcel or another exam board?
17. Re: Very annoying c1 question
aww man I can't do this one...

can anybody help here?

oh actually. I've got an idea, give me a sec.
Last edited by Pride; 12-05-2012 at 20:21.
18. Re: Very annoying c1 question
what were the answers, i got (9,-7) and (-3,17) by setting up a circle centre (3,5) of radius 6root5, and then i sub y=-2x+11 into

(x-3)^2 = (y-5)^2 = 180 to equate the lines and then solved?
Last edited by IAmMclovin; 12-05-2012 at 20:39.
19. Re: Very annoying c1 question
(Original post by Pride)
aww man I can't do this one...

can anybody help here?
I checked my answer and this seems right: set up a circle centre A(3,5) with radius 6root5 to get formula (x-3)^2 +(y-5)^2 = 180, then sub in y=-2x +11 to solve
20. Re: Very annoying c1 question
(Original post by IAmMclovin)
what were the answers, i got (9,-3) and (-7,17) by setting up a circle centre (3,5) of radius 6root5, and then i sub y=-2x+11 into

(x-3)^2 = (y-5)^2 = 180 to equate the lines and then solved?
yeah, when you draw it, it's a lot easier to see that it's a circle.