Refer to the following:
When an airplane flies faster than the speed of sound, the sound waves that are formed take on a cone shape, and where the cone hits the ground, a sonic boom is heard. If $\theta$ is the angle of the vertex of the cone, then $\sin \left(\frac{\theta}{2}\right)=\frac{330 \mathrm{m} / \mathrm{sec}}{V}=\frac{1}{M},$ where $V$ is the speed of the plane and $M$ is the Mach number. (FIGURE CAN'T COPY)
Sonic Booms. What is the Mach number if the plane is flying at 990 meters per second?