Find the Exact Value of the Expression Using the Provided $\mathrm { m }$

Multiple Choice

Find the exact value of the expression using the provided information.
-An airplane flying faster than the speed of sound creates sound waves that form a cone. If vertex angle of the cone and $\mathrm { m }$ is the Mach number for the speed of the plane, then $\sin \frac { \theta } { 2 } = \mathrm { m }$ $( \mathrm { m } > 1 )$ . Find the Mach number to the nearest tenth if $\theta = 30 ^ { \circ }$ .

A) $3.9$
B) $4.5$
C) $3.7$
D) 5