Math Is Fun Forum

ihatecircles

Guest

Circle theorem help?!?!

hi,

http://www.warlinghamschool.co.uk/userfiles/files/Higher%20Non%20Caluclator%20Practice%202.pdf

(go to question 17 in this link)

i have no idea how to approach this problem? i know some circle theorems, for tangents, angles subtended by a chord, etc, but i dont know what to do AT ALL for this!

if anyone could help me that wud be great, thank you.

i only need help on part (a), not part (b). part (b) i can do, cause its a cyclic quadrilateral but i can only do THAT one if i have the answer to part (a)!!

thanks

ihatecircles

Guest

Re: Circle theorem help?!?!

is the answer 57°? because of the "angle in a semi-circle" theorem? just popped into my head

Bob

Administrator

Registered: 2010-06-20

Posts: 10,649

Re: Circle theorem help?!?!

Hi ihatecircles

Yes 57 is right!  You correctly remembered that the angle in a semi circle (PRQ)  is 90.

And PQRS is a cyclic quadrilateral (quad with 4 points all on a circle) so opposite angles add to 180.  That should take care of the second part.

edit: Sorry I've just read all of your post and you already knew this bit.  So you didn't really need help at all.  That's very good.  When are you sitting the exam?

Meanwhile ....  how have you got on with the rest of this paper?

Bob

Last edited by Bob (2010-12-02 08:46:11)

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

ihatecircles

Guest

Re: Circle theorem help?!?!

hi bob bundy,

thanks for your help..i think i can answer the rest of the paper 100% correct. the answer to 21(b) is diagram B right?

i had no trouble with the rest of the paper am sitting a paper soon in a few weeks so just practicing , its just sometimes some years they give you a really easy paper but with one weird question so i wanna be prepared.

thanks

Bob

Administrator

Registered: 2010-06-20

Posts: 10,649

Re: Circle theorem help?!?!

Hi ihatecircles

You are very welcome.  Great to hear that (i) you are practising and (ii) you're doing well with past papers.  [Can you spot I'm a teacher; retired ?]

Your answer to Q21b is correct.

Is it the actual Edexcel exam or just a school 'mock' that is coming up.  I didn't think there were any maths GCSEs  until May/June, but I'm not so in touch with the timetables as I used to be so I may be getting it wrong.

Have you also got access to the answers for past papers?  The last 6 questions on higher papers are pretty mean (after all they don't give away A*s do they?).  No insult intended but you might thinking you've done a question, but actually got it wrong. 

I don't mind if you want to post other answers to check they are right.

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

ihatecircles

Guest

Re: Circle theorem help?!?!

hi bob bundy

well...i havent got the mark scheme, but I have checked my answers using websites like wolfram alpha (for the graph questions) and really if all the stuff i have researched to check my answers is correct then theres no reason why it should be false...

its a school mock, but they tell us to treat it like a real exam,because if you cant show up for the real one due to illness they use the mock grade.

tbh i dont like how they give us 3 days of revision..but i will do my best

thanks for your help!

Bob

Administrator

Registered: 2010-06-20

Posts: 10,649

Re: Circle theorem help?!?!

Good luck!

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob