The chain rule

If u is a function of x and y is a function of u, then the chain rule is -mathformula not MarkupType-
Fatal error: Uncaught Error: Call to undefined method mathformula::makeTypeDef() in /var/www/vhosts/ent.storkey.uk/html/inc/reporting2.php:365 Stack trace: #0 /var/www/vhosts/ent.storkey.uk/html/inc/dynaPage.php(189): echo_value('thechainrule', 'content', Array) #1 /var/www/vhosts/ent.storkey.uk/html/inc/dynaPage.php(742): dynaPage->echo_value('content') #2 /var/www/vhosts/ent.storkey.uk/html/inc/dynaPage.php(179): mainPanel->write('main-panel') #3 /var/www/vhosts/ent.storkey.uk/html/index.php(21): dynaPage->write() #4 {main} thrown in /var/www/vhosts/ent.storkey.uk/html/inc/reporting2.php on line 365