Given that XY is a line segment with the angle a= 21 and c = 33 work out the value of the angle marked b

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?

What is the missing constant term in the perfect square that starts with x^2 -20x

Which is the equation of a line perpendicular to the line with the equation 3x+4y=8