Solve the Problem $\mathrm { E }$ In an Electrical Circuit Is Given By

Multiple Choice

Solve the problem.
-The voltage $\mathrm { E }$ in an electrical circuit is given by $\mathrm { E } = 1.9 \cos 140 \pi \mathrm { t }$ , where $\mathrm { t }$ is time measured in seconds. Find the period.

A) $70 \pi$
B) 70
C) $\frac { 1 } { 70 }$
D) $\frac { \pi } { 70 }$