Suppose we want to choose 5 letters, without replacement, from 14 distinct letters. (a) How many ways can this be done, if the order of the choices matters?
Х
(b) How many ways can this be done, if the order of the choices does not matter?

answer: the angel abc is 30°,and the abc is a triangle where the angel bac is 90°

so ac is the half of 24=12ft,and from the pythagorean theorem we find ba

ba=√bc^2-ac^2=√576-144=√432=12√3ft

so bac is 12+12√3=12(1+√3)ft

the awnser is visionary

the formula of a midpoint between a abd b:

tayeserqp p201311