Given that:
Cos θ = Sin 2θ
⇛ Cos θ = 2 Sin θ Cos θ
⇛ Cos θ / Cos θ = 2 Sin θ
⇛ 1 = 2 Sin θ
⇛ 1/2 = Sin θ
⇛ Sin θ = 1/2
⇛ Sin θ = Sin 30°
⇛ θ = 30°
Therefore, θ = 30°
Answer :-The value of θ for the given problem is 30°
Check:-
LHS = Cos θ
⇛ Cos 30°
⇛ √3/2
RHS = Sin 2θ
⇛ Sin (2×30°)
⇛ Sin 60°
⇛ √3/2
LHS = RHS is true for θ = 30°
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