#1**+1 **

Note that the sine of an angle is just opposite side / hypotenuse

Here.....the opposite side = 11.8 and the hypotenuse =12

So...we need to use the sine inverse (arcsin) function to determine the angle this makes with the ground

arcsin ( 11.8 / 12) = angle measure = 79.5°

So....the ladder is not safe with this angle

Here's a pic :

CPhill Feb 21, 2018