Wordpress header external php file - change title?

Wordpress header external php file - change title?

i have an external php file which i m loading the wordpress header and
footer into which works fine but does anyone have any ideas how you can
change the page title?
/* Short and sweet */
define('WP_USE_THEMES', false);
require('/home/reboot/public_html/wp-blog-header.php');
// get wordpress header
get_header();