| 71. | 
                                    The measure of the angle between x + 2y + z = 1 and  is _____ .
                                 
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| Answer: Option (a) | 
| 72. | 
                                    The measure of the angle between the planes ax + by + d = 0 and z = 0 (a2 + b2 ≠ 0) is _____ .
                                 
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| Answer: Option (d) | 
| 73. | 
                                    The normal to the plane x + 2y + 3z = 6 is _____ .
                                 
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| Answer: Option (b) | 
| 74. | 
                                    The measure of the angle between the plane  and the line  is _____ .
                                 
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| Answer: Option (a) | 
| 75. | 
                                    The perpendicular distance between the plane 6x - 3y + 2z = 1 and 12x - 6y + 4z = 21 is _____ .
                                 
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| Answer: Option (d) | 
| 76. | 
                                    The equation of the plane passing through the points (3, 4, 2), (2, 2, -1) and (7, 0, 6) is _____ .
                                 
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| Answer: Option (a) | 
| 77. | 
                                    If the plane intersect the axes at A, B and C and the centroid of Δ ABC is (1, 3, 1), the equation of the plane is _____ .
                                 
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| Answer: Option (b) | 
| 78. | 
                                    If the perpendicular from the origin to the plane makes angles of equal measures with  and its length is , then what is the equation of the plane ?
                                 
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| Answer: Option (c) | 
| 79. | 
                                    The equation of the plane passing through(1,-4,5) and having normal   (3,1,-1) is _____ .
                                 
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| Answer: Option (a) | 
| 80. | 
                                    The perpendicular distance of the point (3, 2, 1) from the plane 3x + 4y - 2z - 10 = 0 is _____ .
                                 
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| Answer: Option (a) |