Logaritmus: výpočet

Logaritmus kladného čísla x při základu a je takové reálné číslo y = \log_a(x), pro které platí a^y = x. Příklady:

\log_{10}(100) = 2	protože 10^2 = 100
\log_2(32) = 5	protože 2^5 = 32
\log_5(125) = 3	protože 5^3 = 125
\log_7(1) = 0	protože 7^0 = 1
\log_2(0{,}5) = -1	protože 2^{-1} = \frac{1}{2} = 0{,}5

Fatal error: Uncaught TypeError: App\Service\PsService::getUserItemStatusByPs(): Argument #1 ($user) must be of type int, null given, called in /var/www/umimematiku.cz/webroot/src/Snippet/Exercise/ItemBasedExercise/ItemBasedExercisePlugin.php on line 66 and defined in /var/www/umimematiku.cz/webroot/src/Service/PsService.php:69 Stack trace: #0 /var/www/umimematiku.cz/webroot/src/Snippet/Exercise/ItemBasedExercise/ItemBasedExercisePlugin.php(66): App\Service\PsService->getUserItemStatusByPs() #1 [internal function]: App\Snippet\Exercise\ItemBasedExercise\ItemBasedExercisePlugin->progress() #2 /var/www/umimematiku.cz/webroot/src/Helper/ExerciseHeaderBuilder.php(20): call_user_func() #3 /var/www/umimematiku.cz/webroot/src/Template/BaseExercise/default.php(26): App\Helper\ExerciseHeaderBuilder->render() #4 /var/www/umimematiku.cz/webroot/src/Controller/BaseExercise.php(119): require('...') #5 /var/www/umimematiku.cz/webroot/exercise/kalkulacka.php(21): App\Controller\BaseExercise->renderDefault() #6 /var/www/umimematiku.cz/webroot/index.php(109): include('...') #7 {main} thrown in /var/www/umimematiku.cz/webroot/src/Service/PsService.php on line 69