If sinθ1+sinθ2+sinθ3=3, then cosθ1+cosθ2+cosθ3=
(0)
Since sinθ∈[-1,1]
and sinθ1+sinθ2+sinθ3=3
⇒ each sinθ=1
∴ each cosθ=0
Hence, cosθ1+cosθ2+cosθ3=0