I'd assume the recipient 'Simon Plouffe' here is identical to a co-discoverer of the miraculous hexadecimal pi spigot algorithm. https://en.wikipedia.org/wiki/Bailey%E2%80%93Borwein%E2%80%93Plouffe_formula That's so awesome :). On 9/30/19 0:49 , françois mendzina essomba2 wrote:

k*Pi/2=-(sum(((-sqrt(-4*cos((c+a)*x)*cos((d+b)*x)+cos((d+a)*x)^2+2*cos((c+b)*x)*cos((d+a)*x)+cos((c+b)*x)^2)+cos((d+a)*x)+cos((c+b)*x))^n*(sin((d-c)*n*x)+sin((b-a)*n*x)))/(n*2^n*cos((d+b)*x)^n),n=1..infinity))+(c+a)*x;

k in Z

a,b,c,d in R

when sqrt(delta) exist in R