- Forums
###### AL Maths Question-need some help!

Watch

2 months ago

The diagram shows the sector OAB of a circle with centre O, radius 12cm and angle 1.2 radians. The line AC is a tangent to the circle with centre O, and OBC is a straight line. The region R is bounded by the arc AB and the lines AC and CB. The line BD is parallel to AC. Find the perimeter of DAB.

(Will try to add a pic of the diagram) q16.png - OneDrive

This question is from Edexcel year 2 Maths chapter 5 exercise 5D

(Will try to add a pic of the diagram) q16.png - OneDrive

This question is from Edexcel year 2 Maths chapter 5 exercise 5D

(edited 2 months ago)

Original post by pigeonwarrior

The diagram shows the sector OAB of a circle with centre O, radius 12cm and angle 1.2 radians. The line AC is a tangent to the circle with centre O, and OBC is a straight line. The region R is bounded by the arc AB and the lines AC and CB. The line BD is parallel to AC. Find the perimeter of DAB.

(Will try to add a pic of the diagram) q16.png - OneDrive

This question is from Edexcel year 2 Maths chapter 5 exercise 5D

(Will try to add a pic of the diagram) q16.png - OneDrive

This question is from Edexcel year 2 Maths chapter 5 exercise 5D

Should be some straightorward trig? Cant see your images, but just try and describe what you did/what the problem is.

Reply 2

2 months ago

Original post by mqb2766

Should be some straightorward trig? Cant see your images, but just try and describe what you did/what the problem is.

I don't know how to figure out line DA and line BD. Arc AB is easy as it is just 12 x 1.2 which is 14.4. The perimeter of DAB would be arc AB+line BD+line DA and I'm confused about the last two. I looked at the solution bank and yes they are using basic SOH CAH TOA to figure out the lengths of BD and DA but how can they assume that OD is the same as OA (OA is the base of the triangle and that is 12cm). D cuts OA at one point so OD is obviously smaller than OA. But they are assuming that OD is 12cm like OA and that is where I am confused.

Original post by pigeonwarrior

I don't know how to figure out line DA and line BD. Arc AB is easy as it is just 12 x 1.2 which is 14.4. The perimeter of DAB would be arc AB+line BD+line DA and I'm confused about the last two. I looked at the solution bank and yes they are using basic SOH CAH TOA to figure out the lengths of BD and DA but how can they assume that OD is the same as OA (OA is the base of the triangle and that is 12cm). D cuts OA at one point so OD is obviously smaller than OA. But they are assuming that OD is 12cm like OA and that is where I am confused.

You have the right triangle ODB which has hypotenuse 12 and angle 1.2 rad. So you can get OD and BD, and the former gives AD by subtracting it from the radius OA

Reply 4

2 months ago

Original post by mqb2766

You have the right triangle ODB which has hypotenuse 12 and angle 1.2 rad. So you can get OD and BD, and the former gives AD by subtracting it from the radius OA

How do you know that the hypotenuse is 12?

Original post by pigeonwarrior

How do you know that the hypotenuse is 12?

OB is a radius = 12

Reply 6

2 months ago

Original post by mqb2766

OB is a radius = 12

https://qr.ae/pKwQEu

Here is the question with the diagram. Also, would it be that OC is 12 rather than OB? I'm a bit stuck on this one!

edit: I also included the solutions which are not really making sense to me

(edited 2 months ago)

Original post by pigeonwarrior

https://qr.ae/pKwQEu

Here is the question with the diagram. Also, would it be that OC is 12 rather than OB? I'm a bit stuck on this one!

edit: I also included the solutions which are not really making sense to me

Here is the question with the diagram. Also, would it be that OC is 12 rather than OB? I'm a bit stuck on this one!

edit: I also included the solutions which are not really making sense to me

OA is a radius just like OB, after all AB is an arc of the circle. A bit like the other question, youre overthinking it. OBD is a right triange where the hypotenuse OB is a radius = 12. Then its simple trig to get the other two sides ...

(edited 2 months ago)

Reply 8

2 months ago

Original post by mqb2766

OA is a radius just like OB, after all AB is an arc of the circle. A bit like the other question, youre overthinking it. OBD is a right triange where the hypotenuse OB is a radius = 12. Then its simple trig to get the other two sides ...

I see it now, thank you so much!!!

- Bristol Maths Test for Engineering Courses
- A level choices for medicine
- Computer Science in university without doing A Level Maths?
- How math based is A Level Economics? Is Business A Level worth it?
- Good online resources for A-Level Chemistry self-study?
- A-Level Revision Websites
- A level done in year 11
- D1 Edexcel FM Resources?
- Sixth form subject
- Mathematics at Oxford
- A-level Maths
- Will I be able to complete the work in time?
- chemistry books
- can i get a grade 8?
- Which career route is best?
- Studying an MBA after studying a degree in sociology
- Help!!! Should i do cie or edexcel a level maths??
- AQA A Level Chemistry 2021 Assessment Material Unofficial mark scheme
- gcse options for accounting
- Architecture subject requirements???

- Official: University of Nottingham A100 2024 Entry Applicant thread
- Student needs help - BCU radiography
- CTAM: Count to a million (Part 79)
- New spiritual insights, karma, Loa
- Advice on third subject choice?
- Leeds diagnostic radiography interview
- gcse physics
- Mphil Development Studies
- PWC Flying Start Degree Apprenticeships 2024!
- Heyyy
- Official Cambridge Postgraduate Applicants 2024 Thread
- Mst in English (all streams)
- Boy problems!!
- Official Bath Spa University Applicant Thread for 2024
- i like my boy bestfriends
- AQA AS Physics - June 2022 - Paper 2 Question 4.4 - struggling
- Cambridge Sixth Form Law Conference 2023 (CSFLC)
- 2024/2025 Term Dates
- Lloyds Banking Group 2024 Graduate Scheme
- Student finance

- Official Dental Hygiene and Therapy (Oral Health Science) 2024 Entry Thread
- Rothschild Pioneer Work Experience Programme 2024
- Hpe ucl 2024
- Maintenance Loan and Universal Credit
- Why are most women taken or doesnt like me?
- Morgan Stanley Degree Apprenticeship London 2024
- The Trinity!
- Enquiry about swapping courses
- TSR Study Together: French!!
- Teeside Uni Dental Hygiene & Therapy 2022
- GCSE Physics Question Help
- [Official thread] Durham University 2024 Applicants
- DWP Work Coach Interview - how long to hear
- RCSI 2024 Entry Applicants
- Male boundaries and sexuality
- Is this workplace bullying?
- Student finance
- Peeing
- MSc Social Science of the Internet 2024-25
- Supercurriculars for Oxbridge Literature

- GCSE Mathematics Study Group 2023-2024
- A-level Mathematics Study Group 2023-2024
- Mock set 4 paper 2 q14 a level maths (4 distinct points)
- UKMT Intermediate Math Challenge 2024 - Discussion
- Help with complex summation further maths a levels
- Could I have some help with this suvat question?
- MAT practice
- Alevel Maths Question
- weird cosine question
- Series function not differentiable at a point

- hyperbolic function catenary problem
- can anyone answer this A level vectors question (very challenging)
- STEP foundation module help pls
- Ukmt IMC 2024
- ukmt imc
- This maths question is driving me crazy
- Maths Mechanics
- Confused on surds question
- HNC MATHS A2 Task 3 (Radio Transmitters)
- Senior Maths Challenge 2023

- GCSE Mathematics Study Group 2023-2024
- A-level Mathematics Study Group 2023-2024
- Mock set 4 paper 2 q14 a level maths (4 distinct points)
- UKMT Intermediate Math Challenge 2024 - Discussion
- Help with complex summation further maths a levels
- Could I have some help with this suvat question?
- MAT practice
- Alevel Maths Question
- weird cosine question
- Series function not differentiable at a point

- hyperbolic function catenary problem
- can anyone answer this A level vectors question (very challenging)
- STEP foundation module help pls
- Ukmt IMC 2024
- ukmt imc
- This maths question is driving me crazy
- Maths Mechanics
- Confused on surds question
- HNC MATHS A2 Task 3 (Radio Transmitters)
- Senior Maths Challenge 2023

The Student Room and The Uni Guide are both part of The Student Room Group.

© Copyright The Student Room 2024 all rights reserved

The Student Room and The Uni Guide are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: Imperial House, 2nd Floor, 40-42 Queens Road, Brighton, East Sussex, BN1 3XB