Exponential and trigonometric functions practice question 15

Which standard limit about $\sin u$ as $u \to 0$ could help here, and what must be true of its argument? The tangent will need rewriting before it fits.

Write $\tan(4x) = \dfrac{\sin(4x)}{\cos(4x)}$. The limit $\lim_{u \to 0}\dfrac{\sin u}{u} = 1$ needs the same argument on top and bottom.

Multiply and divide so that $\sin(3x)$ sits over $3x$ and $\sin(4x)$ over $4x$.