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

1 Answer
Jul 6, 2018

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