# How do you find the domain and range for y = 3 cos 4x?

Domain: $x =$all real numbers
Range: $\left[- 3 , 3\right]$ or $- 3 \le x \le 3$
Domain: $x =$all real numbers (normal cos function so no domain restrictions.)
Range: $\left[- 3 , 3\right]$ or $- 3 \le x \le 3$ (Amplitude is 3.)