+118658
tan(20-θ)=3 // -180 ≤ θ ≤ 180 degrees
atan(3) = 71.565051177078
\(20-\theta = 71.5650 \pm 180N\\ -\theta = 51.5650 \pm 180N\\ \theta = -51.5650 \pm 180N\\ \text{Now with given restriction}\\ \theta = -51.5650 \quad OR \quad -51.5650 + 180\\ \theta = -51.565^\circ \quad OR \quad \theta=126.435^\circ \\\)
