<s>[INST] Find the value of expression $\frac{1}{\cos 290^{\circ}} + \frac{1}{\sqrt3 \sin250^{\circ}}$. 
Find the value of expression $\frac{1}{\cos 290^{\circ}} + \frac{1}{\sqrt3 \sin250^{\circ}}$.

Though this question seems easy, I just seem to get stuck somewhere. This is what I have tried so far:
$$\frac{1}{\cos70^{\circ}}-\frac{1}{\sqrt3\sin70^{\circ}}$$
$$=\frac{\sqrt3\sin70^{\circ}-\cos70^{\circ}}{\sqrt3\sin70^{\circ}\cos70^{\circ}}$$
From here, I do not know how to continue. Pls help. Thank you :)
 [/INST] $$\frac{\sqrt{3}\sin 70^\circ-\cos 70^\circ }{\sqrt{3}\sin 70^\circ \cos 70^\circ}=\frac{\frac{\sqrt{3}}{2}\sin 70^\circ-\frac{1}{2}\cos 70^\circ }{\frac{\sqrt{3}}{2}\sin 70^\circ \cos 70^\circ}=$$
$$=\frac{\sin 70^\circ \cos 30^\circ -\sin 30^\circ\cos 70^\circ }{\frac{\sqrt{3}}{4}(2\sin 70^\circ \cos 70^\circ)}=\frac{\sin (70^\circ - 30^\circ)}{\frac{\sqrt{3}}{4}(\sin 140^\circ)}=\frac{\sin 40^\circ}{\frac{\sqrt{3}}{4}(\sin 40^\circ)}=\frac{4}{\sqrt{3}}.$$
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