TeX source:

\mathbf{D}\left(\frac{\sin \left(x^{2}\right)}{2 x}\right)=\frac{2 x \cdot \mathbf{D}\left(\sin \left(x^{2}\right)\right)-\sin \left(x^{2}\right) \cdot \mathbf{D}(2 x)}{(2 x)^{2}}=\cos \left(x^{2}\right)-\frac{\sin \left(x^{2}\right)}{2 x^{2}}