Please help. We have this for homework.

Find the lengths of the diagonals of this trapezoid.

Determine the mean and variance of the random variable with the following probability mass function. f(x)=( 729divided by 91) (1 divided by 9) superscript x baseline comma x equals 1,2,3 round your answers to three decimal places (e.g. 98.765).

We just started the introduction into circles and i have no idea how to do this.