What is the missing angle of the triangle 48° 58°

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?

Write an algebraic expression for the word expression the quotient of c and 8

Which of the following expressions is equal to 2x^2+8