Whats the answer, I learned this a while ago, but can't remember how to do it.

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 the sine and cosine values of a, b, respectively, in the figure for (1) and (2) + explanation.

To decrease an amount by 16% what single multiplier would you use