StudioPress: add meta tag to every page [closed]

This function should take care for the input into the head of each page/post as asked.

Please make a copy of functions.php before adding following code.
Adjust to your own preferences if needed.

/**
 * Add meta to head
 *
 * Read more {@link https://codex.wordpress.org/Plugin_API/Action_Reference/wp_head} 
 * @version WordPress 4.8
 */
function wpse272951_wsm_keep_ie_modern() 
{
    echo "<meta http-equiv=\"X-UA-Compatible\" content=\"IE=edge\"/> \n";
} 
add_action( 'wp_head', 'wpse272951_wsm_keep_ie_modern' );

PS, it should not be added into the header as mentioned by you but into the head of a page between <head> </head> (which will be done by this function automatically).