∵ Θ∈(π/2,3π/2)
∴sinΘ=a<0 sinΘ>0 cosΘ<0 sinΘ>|cosΘ|
∵(sinΘ+cosΘ)^2=1+sin2Θ=a+1
∴sinΘ+cosΘ=∫(a+1)