You are Here: Home >< Maths

# IAL differentiation(?) question Watch

1. The height of sea water, h metres, on a harbour wall at time t hours after midnight is given by
h = 3.7 + 2.5cos(30t – 40)°, 0 < t < 24

(a) Calculate the maximum value of h and the exact time of day when this maximum first occurs.

Fishing boats cannot enter the harbour if h is less than 3

(b) Find the times during the morning between which fishing boats cannot enter the harbour. Give these times to the nearest minute

Okay, how on Earth are you supposed to do this?
2. (Original post by jessyjellytot14)
The height of sea water, h metres, on a harbour wall at time t hours after midnight is given by
h = 3.7 + 2.5cos(30t – 40)°, 0 < t < 24

(a) Calculate the maximum value of h and the exact time of day when this maximum first occurs.

Fishing boats cannot enter the harbour if h is less than 3

(b) Find the times during the morning between which fishing boats cannot enter the harbour. Give these times to the nearest minute

Okay, how on Earth are you supposed to do this?
You should be familiar with these sort of Rcos(x - a) questions.

Cosine is bounded between -1 and 1.

-2.5 < 2.5 cos (anything) < 2.5

So 3.7 -2.5 < 3.7 + 2.5 cos (anything) < 3.7 + 2.5

That's yur maximum right there. This occurs when cos (anything) = 1 (for part(b)) so solve thatz.
3. (Original post by Zacken)
You should be familiar with these sort of Rcos(x - a) questions.

Cosine is bounded between -1 and 1.

-2.5 < 2.5 cos (anything) < 2.5

So 3.7 -2.5 < 3.7 + 2.5 cos (anything) < 3.7 + 2.5

That's yur maximum right there. This occurs when cos (anything) = 1 (for part(b)) so solve thatz.
Oh okay, so is it basically a graph transformation question where y=h and x=t ?
4. (Original post by jessyjellytot14)
Oh okay, so is it basically a graph transformation question where y=h and x=t ?
If you want to think of it that way, yeah.

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: May 21, 2016
Today on TSR

### Falling in love with him

But we haven't even met!

### Top study tips for over the Christmas holidays

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Useful resources

### 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

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• 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

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