How to solve Cos(3x)-Cos(2x)+Cos(x)=0 ?

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Answer 1 · 2018-07-06T01:17:49

#Cos(3x)-Cos(2x)+Cos(x)=0#

#=>Cos(3x)+Cos(x)-Cos(2x)=0#

#=>2Cos(2x)Cos(x)-Cos(2x)=0#

#=>Cos(2x)(2Cos(x)-1)=0#

When
#cos2x=0#

#=>2x=(2n+1)pi/2" where " ninZZ#

#=>x=(2n+1)pi/4" where " ninZZ#

When

#(2Cos(x)-1)=0#

#cos(x)=1/2=cos(pi/3)#

#=>x=2kpipmpi/3"where "k in ZZ#