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Question 4 3 pts Find a Cartesian equation for the curve described by the given polar equation r = 2 cos 0 - 4 sin 0 Refer: Converting points between the coordinate system and polar system O (20 - 1)2 + (y - 2)2 = 5 O (2 - 2)2 + (y - 2)2 = 4 O ( 2 + 3) 2 + ( y - 2)2 = 4 O (x - 1)2 + (y - 4)2 = 16Question 7 5 pts Show that the equation x2 + 92 + 22 - 4x + 6y - 4z =10 represent a sphere. Find its center. Refer. Equation of Sphere O Cetner at (1, 4, 9) O Center at (2, -3, 2) Center at (4, - 1, 3) O Center at (1, 2, -1)D Question 8 5 pts Find the angle between the vectors v1 = and v2 = Refer: angels between vectors