Greatest common factor of 21,30

What is the product of the radical expression. (7-2square root) (8+2 square root)

Alex drew a circle with right triangle prq inscribed in it, as shown below: the figure shows a circle with points p, q, and r on it forming an inscribed triangle. side pq is a chord through the center and angle r is a right angle. arc qr measures 80 degrees.

Acircle has a circumference of 28.36 units what is the diameter of the circle