Solution :
We know, cot 2θ = 1/tan 2θ
Multiplying tan 2θ both side of the given equation.
tan²2θ - 3tan 2θ - 10 = 0
tan²2θ - 5tan 2θ + 2tan 2θ - 10 = 0
tan 2θ ( tan 2θ - 5 ) + 2 ( tan 2θ - 5 ) = 0
tan 2θ = -2 or tan 2θ = 5
Therefore, [tex]\theta = \dfrac{tan^{-1} (-2)}{2}[/tex] or [tex]\theta = \dfrac{tan^{-1} (5)}{2}[/tex]
Hence, this is the required solution.
