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# C3 Maths Help Needed

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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

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