For reference: In the figure, AOB is a quadrant and the quadrilaterals OMNL and LTQK are square.
My progress..I would like a solution by geometry...by trigonometry it is solved: $\triangle QOL: \frac{r}{\sin45}=\frac{r\sqrt2}{2\sin 2\theta} \implies \sin2\theta =\frac{1}{2} \therefore \theta = 15^\circ$


