设最小边长为a,等比为q
=>a^2+(aq)^2=(aq^2)^2=a^2q^4
=>1+q^2=q^4
=>q^2=(-1+根号5)/2
较小锐角的正弦值=a/aq^2=1/q^2=1/[(-1+根号5)/2]=(1+根号5)/2