MATLAB has many built in functions and numbers. One of those is a built in representation of the number $\backslash$pi $,3\mathrm{.}14159...$ In MATLAB, you just need to write $$pi$$ to access that number. While that number is not $100\%$ accurate $($no representation of pi is$),$ it has many more decimal places, and is much more accurate, than the approximation we sometimes use for rough calculations by hand, $3\mathrm{.}14$