$\int \cos 2 x^{\circ} d x=$ কত ?

$2 \sin 2 x^{\circ}+c$

$\frac{\sin 2 x^{\circ}}{2}+c$

$\frac{90^{\circ}}{\pi} \sin 2 x^{\circ}+\mathrm{c}$

$\frac{90}{\pi} \sin \frac{\pi x}{180^{\circ}}+c$