How is a tangent different from a chord

For each expression use a property to write an equivalent expression.

Iam so stuck. what is the worked out answer for this question?

If the speed of an electromagnetic wave is 100,000 cm/s and its wavelength is 100 cm, what is its frequency? a) 100,000 cycles per second (hz) b) 1 × 10-3 cycles per second (hz) c) 10,000,000 cycles per second (hz) d) 1,000 cycles per second (hz)