$\"\"$

The general form of cosine function is $\"\"$ .

Where $\"\"$ is amplitude and $\"\"$ is period.

The time period is $\"\"$ .

The distance between the highest and lowest points is $\"\"$ centimeters,Therefore $\"\"$ .

Hence Amplitude $\"\"$ .

The time period to completed one cycle is $\"\"$ seconds.

Therefore $\"\"$

$\"\"$

Subtitute $\"\"$ and $\"\"$ in $\"\"$ .

The cosine function is $\"\"$ .

$\"\"$

The cosine function is $\"\"$ .