Find the number of solutions for cos y=cosx.
When cos y=cosx , solution of the equation is
y = 2nπ ± x
So, cosy=cosx, represents two sets of straight lines;
y = x + 2nπ ;n ϵ z
= −x + 2nπ ;n ϵ z
Graph of cosy=cosx
i.e. two infinite set of perpendicular straight lines which could be shown in the figure.
Thus, graph for cos y=cosx; represents two perpendicular straight lines which have infinite number of points of intersection; so, number of solutions are infinite