## Trigonometry (11th Edition) Clone

$$\cos42^\circ=\cos(30^\circ+12^\circ)$$ The statement is true.
$$\cos42^\circ=\cos(30^\circ+12^\circ)$$ Consider $\cos(30^\circ+12^\circ)$ As $30^\circ+12^\circ$ are put inside a parathesis, this means the sum must be carried out first. And since $30^\circ+12^\circ=42^\circ$, $$\cos(30^\circ+12^\circ)=\cos42^\circ$$ The statement is thus true.