275 liters to millimeters

The distance of a chord from the centre of a circle is 12cm and the lenght of the chord is 10cm. find the radius of the circle

Write the equation of the circle centered at (10,-2) with radius 2.

For a short time after a wave is created by wind , the height of the wave can be modeled using y= a sin 2pi(t) / t where a is the amplitude and t is the period of the wave in seconds. how many times over the first 5 seconds does the graph predict the wave to be 2 feet high?