what is pie in terms of wave?
Pi ( π ) is the ratio of the circumference of a circle to its diameter: Pi ( π ) = C/D. It matters not how large or small the circle: this ratio is always the same. Divide a circumference of a circle by its diameter, and you 3.141596535...
It follows from algebraic equivalence then that C = π * D. (The circumference of a circle is equal to the diameter times pi). We get this by multiplying each side of the first equation by D, and the "D's" cancel out on the right side, leaving only the C. Thus C = pi • D.
Since the radius of a circle is half the diameter, it follows that the circumference is equal to 2πR, that is: 2 times the radius times pi (because D is two times the radius).
Since, in a unit circle, the radius is by definition equal to 1, then the circumference of a unit circle is simply 2 pi (2 pi times 1, or just 2π). .
One journey around a circle, 360º is the same as a journey of 2 pi. These are equivalent. A sine wave shows this excursion around a circle happening in time. A sine wave, ultimately, is a circle expressed in time.