Hey there! Sign in to join this conversationNew here? Join for free
 You are Here: Home >< Maths

# FP3 Watch

1. http://pastpapers.download.wjec.co.uk/s15-0979-01.pdf
In 6ci, the mark scheme says x=2sintheta
Like how am i supposed to know that?
2. (Original post by Ayaz789)
http://pastpapers.download.wjec.co.uk/s15-0979-01.pdf
In 6ci, the mark scheme says x=2sintheta
Like how am i supposed to know that?
You want 4-x^2 to turn into a perfect square, so note that 1-sin^2x = cos^2x -> 4-4sin^2x=4cos^2x -> 4-(2sinx)^2=4cos^2x, so change x to 2sintheta as required so that you get 4cos^2theta under the square root, giving 2costheta.
3. It is quite a standard substitution.
4. (Original post by Ayaz789)
http://pastpapers.download.wjec.co.uk/s15-0979-01.pdf
In 6ci, the mark scheme says x=2sintheta
Like how am i supposed to know that?
The biggest hint is that the value of the integral is , so it MUST be a trig substitution, and once you know that the sub is very obvious.
5. This is not really related to FP3, but could someone please explain how to do this question?

"On a clear day, you are on an aeroplane which is at 38,000 ft above the middle of the Pacific ocean. Taking the radius of the earth as 6,400km, what is the approximate distance between you and the horizon of the earth? (1ft=0.3048m)"

Thank You
6. (Original post by SmithAmelia)
This is not really related to FP3, but could someone please explain how to do this question?

"On a clear day, you are on an aeroplane which is at 38,000 ft above the middle of the Pacific ocean. Taking the radius of the earth as 6,400km, what is the approximate distance between you and the horizon of the earth? (1ft=0.3048m)"

Thank You
**

it is a right angled triangle so you can use Pythagoras to find the missing side.*

Reply
Submit reply
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: June 29, 2016
Today on TSR

### What is the latest you've left an assignment

And actually passed?

### Simply having a wonderful Christmas time...

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

## 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
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.