cropping view by changing camera

if i want to render a part of image (like cropping in gimp) how do i change camera location and viewing angle(lens) - is there a formula? e.g. i want to get a new view shown in red rectangle.


CTRL+B and apply Border and Brop in the settings for render (under “aspect ratio”)

thanks.but i would like to do it without using border render.also generally it will be useful to know.