Possible Duplicate:
Prove this inequality: $|a_1b_1+a_2b_2+\cdots+ a_nb_n|\leq 1$ for two normalised vectors
Prove this inequality: $|a_1b_1+a_2b_2+\cdot\cdot\cdot + a_nb_n|\leq 1$
if
$a_1^2+a_2^2+\cdot\cdot\cdot+a_n^2=1$
$b_1^2+b_2^2+\cdot\cdot\cdot+b_n^2=1$