If cos mx = cos nx, m ≠ n,
Question:
If cos mx = cos nx, m ≠ n, then x =______________.
Solution:
If cos mx = cos nx ; m ≠ n
i.e mx = 2rπ ± nx ; r∈Z
i.e x(m ± n) = 2rπ
i.e $x=\frac{2 r \pi}{m \pm n}$