Free 5 points but anyways I'm gonna text someone i haven't texted since 2018. Just to feel something

One expression below in undefined, and the other expression has a well defined value. which expression is undefined and explain why it has no value. which expression is defined? what is the value of that expression and how do you know? what is a different expression using a trig inverse function that is also undefined?

Me! 50 points! why does when we come home, our door is unlocked and there is grease on the door knob, me solve this , and i don't know what category this goes under

Fast! find the length of cu. the triangles are similar. show your work.