Question Number 11087 by suci last updated on 11/Mar/17
$${a}<\frac{\pi}{\mathrm{2}} \\ $$$${if}\:{M}<\mathrm{1}\:{with}\:\mid{cos}\:{x}−{cos}\:{y}\mid\leqslant{M}\mid{x}−{y}\mid \\ $$$${to}\:{each}\:{x},{y}\in\left[\mathrm{0},{a}\right] \\ $$$${M}=….??? \\ $$