14.已知θ₁、θ₂、θ₃三個實數成等差數列,且公差為π/2,其中π為圓周率。若π/2≤θ₁<π且sin²θ₂=9/25,則sin(θ₁+θ₃)之值為何?(A) \(\frac{12}{25}\)(B) \(\frac{-12}{25}\)(C) \(\frac{-24}{25}\)(D) \(\frac{24}{25}\)