Circle Geo Q (1 Viewer)

[Axio]

Hey. So I am stuck on this question because the answers say the first step is that OC bisects AB because they are perpendicular but how do you know that they are perpendicular, as it isn't given? Thanks

 

[Shadowdude]

Is this a 2u or a 3u question?

 

[Axio]

3u

 

[Axio]

This probably should be moved to 3U subforums :/

 

[Shadowdude]

uhh i'm just going to say that's a weird question because they don't give you enough information

Just assume it's perpendicular and go from there, I suppose

 

[Axio]

Ok cool so you agree with me, excellent.

 

[enigma_1]

Hey. So I am stuck on this question because the answers say the first step is that OC bisects AB because they are perpendicular but how do you know that they are perpendicular, as it isn't given? Thanks

View attachment 30175

MATEEEEE They give you enough information!!!

You have to find CO, use Pythagoras for that.

You go CO^2 = BO^2 - BC^2

BO = radius = r

CB = x/2 because it is half of AB.

Use Pythagoras and then you get CO. Then you add your answer for CO to OD (which is r)

You manipulate your answer to make it look like that there.

 

[enigma_1]

The only circle geo logic you use here is the AC=CB because a line subtended from the center of a circle which cuts a chord must cut it in the middle.

 

[enigma_1]

Omg I hope you're not basing your whole mathematics course on Margaret Grove's extensively simple textbook??????? The questions are designed to decrease one's intelligence because they are so simple. I advise you to grab hold of Cambridge mainly and maybe Fitzpatrick as once you do questions from there, questions from Margaret Grove you can do with closed eyes. That woman sucks I swear!

 

[Carrotsticks]

Ok cool so you agree with me, excellent.

Axio, it is a course theorem that if OC bisects AB, then OC is perpendicular to AC.

 

[bongoli]

Hey. So I am stuck on this question because the answers say the first step is that OC bisects AB because they are perpendicular but how do you know that they are perpendicular, as it isn't given? Thanks

View attachment 30175

This is a circle geometry theorem which states that a line connecting the midpoint to a chord to the centre is perpendicular to the chord.

 

[Shadowdude]

The only circle geo logic you use here is the AC=CB because a line subtended from the center of a circle which cuts a chord must cut it in the middle.

No it doesn't:

The red line goes from the centre of a circle to the blue chord, but that doesn't cut it in the middle.

This is a circle geometry theorem which states that a line connecting the midpoint to a chord to the centre is perpendicular to the chord.

Yes, but nowhere in the question does it say "C is the midpoint of AB".

 

[Axio]

No it doesn't:

The red line goes from the centre of a circle to the blue chord, but that doesn't cut it in the middle.



Yes, but nowhere in the question does it say "C is the midpoint of AB".

This ^.

 

[enigma_1]

I did it my way and I got the answer. Guys, Margaret Grove is not really very intelligent, so you have to empathise with her and do the question the way she thinks (which is very 2D and with no depth). But in an exam you would have to be careful.

 

[Shadowdude]

I did it my way and I got the answer. Guys, Margaret Grove is not really very intelligent, so you have to empathise with her and do the question the way she thinks (which is very 2D and with no depth). But in an exam you would have to be careful.

If you make those assumptions, yes - you'll get the question out.

But if you do the question as is, there's not much you can do unless your first line in the proof is "Assume that ....." and whatever it is.

 

[enigma_1]

If you make those assumptions, yes - you'll get the question out.

But if you do the question as is, there's not much you can do unless your first line in the proof is "Assume that ....." and whatever it is.

Yes I agree with you wholeheartedly and that's why Margaret Grove decreases one's intelligence. She makes you make assumptions and in an exam if you "make up" random ideas, then where the fkk is the maths in that? It's more of a psychology textbook if you ask me, the woman teaches you to think of what's going on in her head

https://www.brocku.ca/library/about-us-lib/welcome

 

[Carrotsticks]

I did it my way and I got the answer. Guys, Margaret Grove is not really very intelligent, so you have to empathise with her and do the question the way she thinks (which is very 2D and with no depth). But in an exam you would have to be careful.

I think that's a bit of an unfair statement to make.

Is it possible that her textbook is specifically aimed at lower-end - average students (ie: the majority of students taking the 2U/3U course) so it's been 'dumbed down'?

 

[Axio]

I don't like making assumptions that aren't necessarily true. It's an impossible question IMO (unless it was corrected or some uni maths can solve it)

 

[enigma_1]

I think that's a bit of an unfair statement to make.

Is it possible that her textbook is specifically aimed at lower-end - average students (ie: the majority of students taking the 2U/3U course) so it's been 'dumbed down'?

Yeah ok sorry, that was really mean of me

It is, but whyyyyyy give them a false impression that that's what maths is when it really isn't?! It's abusing the subject which I don't like

Lower end people shouldn't be doing this subject, or should be exposed to real questions like Cambridge.

 

[Carrotsticks]

I don't like making assumptions that aren't necessarily true. It's an impossible question IMO (unless it was corrected or some uni maths can solve it)

The question (in it's current form) is not doable because we need the condition that DC bisects AB.

Yeah ok sorry, that was really mean of me

It is, but whyyyyyy give them a false impression that that's what maths is when it really isn't?! It's abusing the subject which I don't like

Lower end people shouldn't be doing this subject, or should be exposed to real questions like Cambridge.

Ideally, 'lower end' students should not be doing the subject, but this is an imperfect world where people fruitlessly attempt beyond their capabilities for the sake of marks or 'scaling'. What is 'lower end'? One person's 'lower end' may be another's 'higher end'.