I tried writing the problem below but it's hard because it's an integral

Question

The integral of (n)(pi) on the top and (pi) on the bottom of 9cosxdx

Answer 1

Use a markdown editor that accepts LaTeX. For example Rstudio or Emacs or VI.

$$ \int_\pi^{n\pi}{9\cos{x} dx} $$

Answer 2

The antiderivative of 9cos(x) dx is 9sin(x). The definite integral means we plug in the upper and lower limits and subtract them so it equals 9sin(nπ) - 9sin(π) = 9sin(nπ)