BF=6; HF=2.5
p <- function(x) {f <- 0;
for(i in 0:n) f <- f+sin((2*i+1)*x)/(2*i+1); f <- f*4/pi}
n = 0; graph1F(p, -5,10, "black")
n = 1; graph1(p, -5,10, "blue")
n = 2; graph1(p, -5,10, "brown")
n = 10; graph1F(p, -5,10, "seagreen")
n = 80; graph1F(p, -5,10, "red")