sinθ^2＋cosθ^2＋sinθ^2＋cosθ^2=2sinθ^2＋2cosθ^2

(sinθ)^2+(cosθ)^2=1

>>244
log((8/15)^n)=-0.2731n

10^(-6)≦p<10^(-5)
-6≦log(p)<-5