根号(1-sinθ)
=根号[1-2sin(θ/2)*cos(θ/2)]
=根号[sin^2(θ/2)+cos^2(θ/2)-2sin(θ/2)*cos(θ/2)]
=根号{[sin(θ/2)-cos(θ/2)]^2}
=|sin(θ/2)-cos(θ/2)|
由0〈θ〈π/2
当0