solve for between 0 and 2 pal

cos^2 (2X)=cos (2X)

thanks in advance

Printable View

- January 12th 2010, 07:11 PMalessandromangionesolve given general solution
solve for between 0 and 2 pal

cos^2 (2X)=cos (2X)

thanks in advance - January 12th 2010, 07:14 PMpickslides

divide both sides by gives

Can you solve it from here? - January 12th 2010, 08:03 PMalessandromangione
thank u very much...now i can do it!

- January 12th 2010, 08:04 PMdifferentiate
I thought you weren't allowed to divide by cos2x since cos2x might be equal to zero, in which if you divide by cos2x, there will be no solution...

- January 12th 2010, 08:34 PMnikhil
[cos(2x)]^2=cos(2x)

or

[cos(2x)]^2- cos(2x)=0

cos(2x)[cos(2x)-1]=0

cos(2x)=0 or cos(2x)=1

a) if cos(2x)=0 then

2x=pi/2,3pi/2 or

x=pi/4,3pi/4

b)cos(2x)=1 then

2x=0,2pi or

x=0,pi

hence

x=0,pi/4,3pi/4,pi

now 0 may be excluded as interval is0 to 2pi**between**

therefor finally

x= pi/4,3pi/4,pi - January 13th 2010, 03:35 AMHallsofIvy