Draw a triangle

This just cannot be this hard!  I want a side of the triangle to go from 0,0 to the right 297 on the same level.  Then from that corner down 5.25 at 90 degrees.  Then back to 0,0.  Got any help?

https://dokuwiki.librecad.org/doku.php/tutorial:simple_template or https://librecad.readthedocs.io/en/latest/guides/cmdline.html

There are TWO solutions for your problem.
ezgif-3-08990255e17b.gif
Check this out!!!

P.S.: DON'T FORGET TO SEE 'COMMAND LINE' ALSO.