f'(θ) = sin 2θ
f’(θ) = (cos 2θ) (2) = 2 cos 2θ
f”(θ)= 2[-sin 2θ] (2) = – 4 sin 2θ
f”(θ) = 0 ⇒ – 4 sin 2θ = 0
f(θ) is concave upward in the interval ((π/2),π)
So, at θ = π/2 we get a point of inflection. At θ = π/2, f(θ) = sin 2(π/2) = 0
So, the curve is concave upward in ((π/2),π) and concave downward in (0,(π/2)).
The point of inflection is ((π/2),0).