The following analog of Bernstein inequality for monotone rational functions
is established: if $R$ is an increasing on $[-1,1]$ rational function of degree
$n$, then $$ R'(x)<\frac{9^n}{1-x^2}\|R\|,\quad x\in (-1,1). $$ The exponential
dependence of constant factor on $n$ is shown, with sharp estimates for odd
rational functions.
For each $N\ge c_dt^d$ we prove the existence of a spherical $t$-design on
the sphere $S^d$ consisting of $N$ points, where $c_d$ is a constant depending
only on $d$. This result proves the well-known conjecture of Korevaar and
Meyers concerning an optimal order of minimal number of points in a spherical
$t$-design on $S^d$ for a fixed $d$.