If two lines are parallel the lines must they lie on the same plane

Determine whether the quadrilateral below is a parallelogram. justify/explain your answer (this means back it up! give specific information that supports your decision. writing just "yes" or "no" will result in no credit.)

Express the following as a function of a single angle. cos(60) cos(-20) - sin(60) sin(-20)

Will mark name all segments skew to bc