3. The co-ordinates of the centroid of a triangle ABC are (-1 , 4). What are the co-ordinates of vertex C if co-ordinates of A and B are (-3 , -1) and (3 , 5) respectively?
7. The diagonal of a square is equal to the side of an equilateral triangle. If the area of the square is 15?3 sq cm, what is the area of the equilateral triangle?