You are Here: Home >< Maths

# C3 Maths Help Needed Watch

Announcements
1. Show that
cos2x/cosx+sinx = cosx - sinx
:?
Thanks
2. Cos2x = (cosx-sinx)(cosx+sinx)
3. (Original post by Mr Moon Man)
Cos2x = (cosx-sinx)(cosx+sinx)
I dont understand
how does

cos2x = ( cosx + sin x ) ( cosx - sinx)
4. Cos2x = (cosx)^2 - (sinx)^2 = (cosx - sinx)(cosx + sinx)
5. (Original post by Mr Moon Man)
Cos2x = (cosx)^2 - (sinx)^2 = (cosx - sinx)(cosx + sinx)

I get what you did at the end. you just took the difference of two squares but how does
cos2x = (cosx)^2-(sinx)^2
Thank you for helping
6. (Original post by Why-_-Study-_-)
I get what you did at the end. you just took the difference of two squares but how does
cos2x = (cosx)^2-(sinx)^2
Thank you for helping
Have you not done trig identities yet? Cos2x is one of the main ones
7. (Original post by Mr Moon Man)
Have you not done trig identities yet? Cos2x is one of the main ones
I understand it now
Cos ( 2A ) = cos^2 A - sin^2 A

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: October 9, 2016
Today on TSR

### Oxbridge

Even more elitist than everyone thought?

### Physically ill after being cheated on

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.