since tanθ = 3/4 in QIII,
sinθ = -3/5
cosθ = -4/5
since sinϕ = -3/√10 in QIV,
cosϕ = 1/√10
Now you have everything you need to evaluate sin(θ − ϕ)
using your formula.
sin(θ − ϕ);
tan(θ) = 3/4,
θ in Quadrant III,
sin(ϕ) = − (3sqrt 10)/10,
ϕ in Quadrant IV
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