What is the measure of the obtuse angle in this figure?

Its not 180

The table shows the webster family’s monthly expenses for the first three months of the year. they are $2,687.44, $2,613.09, and $2,808.64. what is the average monthly expenditure for all expenses?

Could somebody me with this radical simplification?

If cos(2x) = tan^2(y), show that cos(2y) = tan^2(x).