Turn on thread page Beta
 You are Here: Home >< Maths

# C3 Trig watch

1. Express f(θ) = 5 cos θ + 12 sin θ in the form RCos (θ-α)
I got: 13 cos (θ - 1.176)

part b) Find the smallest possible value of

I'm completely stuck on how to do the second part, for the smallest value it would be -1 not sure how this would help me get the answer, thanks for all the help!
2. (Original post by IgorYakov)
Express f(θ) = 5 cos θ + 12 sin θ in the form RCos (θ-α)
I got: 13 cos (θ - 1.176)

part b) Find the smallest possible value of

I'm completely stuck on how to do the second part, for the smallest value it would be -1 not sure how this would help me get the answer, thanks for all the help!
What does this mean
3. (Original post by TenOfThem)
What does this mean

Sorry I didn't word that properly, for the smallest value for Cos it would be -1 right? So in the case of the 13 cos (θ - 1.176) it would be -13?

Or is this completely different to maximum and minimum values?
4. (Original post by IgorYakov)
Express f(θ) = 5 cos θ + 12 sin θ in the form RCos (θ-α)
I got: 13 cos (θ - 1.176)

part b) Find the smallest possible value of

I'm completely stuck on how to do the second part, for the smallest value it would be -1 not sure how this would help me get the answer, thanks for all the help!

Which value of would force to take on it's smallest value?

Hint
The denominator must be forced to it's maximum, to ensure the fraction given is at it's smallest value.

Further Hint
5. (Original post by IgorYakov)
Sorry I didn't word that properly, for the smallest value for Cos it would be -1 right? So in the case of the 13 cos (θ - 1.176) it would be -13?
Your smallest value of f(theta) = -13

So what are the smallest and largest values of f(theta) + 2
6. (Original post by Khallil)

Which value of would force to take on it's smallest value?

Hint
The denominator must be forced to it's maximum, to ensure the fraction given is at it's smallest value.

Further Hint

Ohh okay so for the maximum of 13 cos (θ - 1.176) it is 13 as the maximum for a cos graph is 1 ?
7. (Original post by TenOfThem)
Your smallest value of f(theta) = -13

So what are the smallest and largest values of f(theta) + 2

Wouldn't you just have one value of -13+2 for the minimum of -13?
8. (Original post by IgorYakov)
Wouldn't you just have one value of -13+2 for the minimum of -13?
-11 is indeed the minimum

what is the maximum
9. (Original post by IgorYakov)
Ohh okay so for the maximum of 13 cos (θ - 1.176) it is 13 as the maximum for a cos graph is 1 ?

Now what does the fact that the maximum value of being 13 tell you about
10. (Original post by Khallil)

Now what does the fact that the maximum value of being 13 tell you about

(Original post by TenOfThem)
-11 is indeed the minimum

what is the maximum

That it's 2

Thanks! I was trying to find the minimum and not the maximum, I didn't realise that because it's on the denominator I needed the maximum for the whole number to be it's smallest

Khallil PRSOM
11. (Original post by Khallil)

Which value of would force to take on it's smallest value?

Hint
The denominator must be forced to it's maximum, to ensure the fraction given is at it's smallest value.

Further Hint
You need to look at the specific question as your hint is not correct in this case
12. (Original post by IgorYakov)
That it's 2

Thanks! I was trying to find the minimum and not the maximum, I didn't realise that because it's on the denominator I needed the maximum for the whole number to be it's smallest
Sorry - where have you got 2 from

That is not the maximum for the denominator nor the answer to the question
13. (Original post by TenOfThem)
Sorry - where have you got 2 from

That is not the maximum for the denominator nor the answer to the question

As it's 13 isn't it just 30/13+2?
14. (Original post by IgorYakov)
As it's 13 isn't it just 30/13+2?
no
15. (Original post by TenOfThem)
no

Ohh ok so what would I do after getting the maximum of 13?
16. (Original post by IgorYakov)
Ohh ok so how what would I do after getting the maximum of 13?
Okay

Look at what I asked you

What are the minimum and maximum values of f(theta) + 2
17. (Original post by TenOfThem)
Okay

Look at what I asked you

What are the minimum and maximum values of f(theta) + 2
minimum -11, maximum 15?
18. (Original post by IgorYakov)
minimum -11, maximum 15?
ok - I always suggest that students consider both ends of the range

So

Which is smaller

30/-11 or 30/15
19. (Original post by TenOfThem)
Sorry - where have you got 2 from

That is not the maximum for the denominator nor the answer to the question
Really?

Spoiler:
Show

To find the smallest value of the given fraction, maximise the value of the denominator.

The maximum value of occurs at

The smallest value of the given fraction is:

20. (Original post by TenOfThem)
ok - I always suggest that students consider both ends of the range

So

Which is smaller

30/-11 or 30/15
30/-11

Reply
Submit reply
Turn on thread page Beta
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: November 15, 2013
Today on TSR

### Which business legend are you?

We have the answer...

### University open days

• University of Roehampton
All departments Undergraduate
Sat, 17 Nov '18
• Edge Hill University
Faculty of Health and Social Care Undergraduate
Sat, 17 Nov '18
• Bournemouth University
Undergraduate Open Day Undergraduate
Sat, 17 Nov '18
Poll
Useful resources

## Make your revision easier

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

Can you help? Study help unanswered threads

## Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.