sinθ+cosθ=根号2
两边平方,1+2sinθcosθ=2
2sinθcosθ=1
2sinθ(根号2－sinθ)=1
2sinθ^2-2根号2sinθ+1=0
sinθ＝根号2/2
cosθ=根号（1-sinθ^2）=根号2/2
log1/2(sinθ)·log1/2(cosθ)
＝(log1/2(根号2/2))^2
＝(log1/2 (1/2)^(1/2))^2
=1/4