أرسل هذا في رسالة قصيرة: Exact solution for buckling of columns including self-weight

導出完成 — 

 _    _      ___     _    _    _    _     _  _   
| \  / ||   / _ \\  | |  | || | || | ||  | \| || 
|  \/  ||  | / \ || | |/\| || | || | ||  |  ' || 
| .  . ||  | \_/ || |  /\  || | \\_/ ||  | .  || 
|_|\/|_||   \___//  |_// \_||  \____//   |_|\_|| 
`-`  `-`    `---`   `-`   `-`   `---`    `-` -`