You are Here: Home >< A-levels

# c4 maths Watch

1. can someone help me with this question?

∫( 4 − x^2)^0.5 dx

x = 2 sinx

limits are 1 and 0
2. What does the 'x = 2 sinx' refer to?
3. (Original post by rebirth61213)
What does the 'x = 2 sinx' refer to?
you have to sub x into the equation as 2sinx
4. (Original post by 619-booyaka)
can someone help me with this question?

∫( 4 − x^2)^0.5 dx

x = 2 sinx

limits are 1 and 0
Do it like any other substitution. Do not forget the limits.
5. (2sinx)^2 = 4*(sinx)^2

(sinx)^2 = 1 - (cosx)^2

Sub that in (I'll leave the rest to you; you should end up with a simple function to integrate).
6. (Original post by ODES_PDES)
Do it like any other substitution. Do not forget the limits.
I don't think he/she meant that this is a 'u-substitution method' question. (why would one want to sub in 2sinx?) I think he/she meant that the x in the above expression is 2sinx and avoided putting that in the top expression in order to maintain clarity (I think).
7. (Original post by rebirth61213)
I don't think he/she meant that this is a 'u-substitution method' question. (why would one want to sub in 2sinx?) I think he/she meant that the x in the above expression is 2sinx and avoided putting that in the top expression in order to maintain clarity (I think).
Take over as I am rusty
8. (Original post by 619-booyaka)
can someone help me with this question?

∫( 4 − x^2)^0.5 dx

x = 2 sinx

limits are 1 and 0
(Original post by rebirth61213)
I don't think he/she meant that this is a 'u-substitution method' question. (why would one want to sub in 2sinx?) I think he/she meant that the x in the above expression is 2sinx and avoided putting that in the top expression in order to maintain clarity (I think).
Maths professors at uni would be ripping their hair out at the line x=2sinx, even if it's just to make representing things easier - there are 25 other letters to choose from! But really, it doesn't matter at this stage
9. arcsin(x/2)=x

∫( 4 − arcsin(x/2)^2)^0.5 dx

there I solved it.

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 28, 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
Help with your A-levels

## All the essentials

### Student life: what to expect

What it's really like going to uni

### Essay expert

Learn to write like a pro with our ultimate essay guide.

### Uni match

Our tool will help you find the perfect course for you

### Create a study plan

Get your head around what you need to do and when with the study planner tool.

### Resources by subject

Everything from mind maps to class notes.

### Degrees without fees

Discover more about degree-level apprenticeships.

### Study tips from A* students

Students who got top grades in their A-levels share their secrets

## Study help links and info

Can you help? Study help unanswered threadsRules and posting guidelines

### HEAR

Find out how a Higher Education Achievement Report can help you prove your achievements.

## 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.