[tex] \cos(2x) = \cos(x) [/tex]
Solution (1)
[tex]2x = x + 2k\pi[/tex]
[tex]2x - x = 2k\pi[/tex]
[tex]x = 2k\pi[/tex]
for k=0 / for k=1 / for k=-1
x=0 / x=2π / x=-2π
acc / acc / rej
solution (2)
[tex]2x = - x + 2k\pi[/tex]
[tex]2x + x = 2k\pi[/tex]
[tex]3x = 2k\pi[/tex]
[tex]x = \frac{2k\pi}{3} [/tex]
for k=0 / for k=1 / for k=-1
x=0 / x=2π/3 / x=-2π/3
acc / acc / rej
Note that i'm trying values of K which make the answer belong to our interval;
So our solution which i will represent as a set is;
S € {0,2π/3,2π}
