can anyone solve this ?

[qshyrn]

this was on the side in the sample exam   cos(x)+cos(3x)=1/2 asking for the general soln

do they expect us to be able to this by hand? 
i Used my Ti89 and it couldnt do it... (only gave approx answers )

the answers meant to be 4pi/3 +2pi*n   which i got from wolfram alpha.

[Stroodle]

http://vcenotes.com/forum/index.php/topic,32364.0.html

[qshyrn]

http://vcenotes.com/forum/index.php/topic,32364.0.html

ok didnt see that.
does anyone know how to get the answer on the calc though???

[VCE123456789]

we dont need to know this its not in the methods course dw

[TrueTears]

http://vcenotes.com/forum/index.php/topic,32364.0.html

ok didnt see that.
does anyone know how to get the answer on the calc though???

type solve(cos(x)+cos(3x)=1/2,x)|0<=x<=4pi (this is the command for TI-89)

this will yield some solutions, then you pick the 2 basic solutions and add periods (the period is the LCM(2pi, 2pi/3))