1/cosθ/2+sinθ/2/cosθ/2=(1+sinθ/2)/cosθ/2
√[(1+sinθ/2)/(1-sinθ/2)]
分子分母同乘1+sinθ/2得
|1+sinθ/2|/√(1-sin²θ/2)
=|1+sinθ/2|/|cosθ/2|
二者相等
∴1+sinθ/2>=0
cosθ/2>0
sinθ/2>=-1恒成立
只需cosθ/2>0
∴-π/2+2kπ
1/cosθ/2+sinθ/2/cosθ/2=(1+sinθ/2)/cosθ/2
√[(1+sinθ/2)/(1-sinθ/2)]
分子分母同乘1+sinθ/2得
|1+sinθ/2|/√(1-sin²θ/2)
=|1+sinθ/2|/|cosθ/2|
二者相等
∴1+sinθ/2>=0
cosθ/2>0
sinθ/2>=-1恒成立
只需cosθ/2>0
∴-π/2+2kπ