Inactive Tutor answered 11/26/16
Tutor
New to Wyzant
The given cosecant value tells you that sine θ = 2/5 and the fact that tangent is negative places the angle θ in quadrant II, where sines are positive but cosines are negative.
cos θ must be -√21/5 using the Pythagorean identity.
From these facts you can easily finish the job.