MEDIUM
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P is the point of concurrency of three straight lines  L1, L2, and L3 which are mutually perpendicular to each other. If one of them intersects the x-axis and other intersects the y-axis, while the third line passes through a fixed point (0, 0, c) on the z-axis, then which of the following options satisfy the locus of the point P ?

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Important Questions on Vectors

MEDIUM
If points P4, 5, x, Q3, y, 4 and R5, 8, 0 are collinear, then the value of x+y is
MEDIUM
If a line makes angles 120o and 60o with the positive directions of X and Z axes respectively then the angle made by the line with positive Y- axis is
HARD
If a variable plane, at a distance of 3 units from the origin, intersects the coordinate axes at A, B & C, then the locus of the centroid of ΔABC is
MEDIUM
Let ABC be a triangle whose circumcentre is at P. If the position vectors A, B, C and P are a,b,c and a+b+c4 respectively, then the position vector of the orthocentre of this triangle, is : 
HARD
Let ABC be an acute scalene triangle, and O and H be its circumcentre and orthocentre respectively. Further, let N be the midpoint of OH. The value of the vector sum NA+NB+NC is
HARD

A line in the 3-dimensional space makes an angle θ 0 < θ π 2 with both the X and Y-axes. Then, the set of all values of θ is in the interval :

EASY
The point in the xy- plane which is equidistant from 2,0,3,0,3,2 and 0,0,1 is
EASY
If a line makes an angle of π4 with the positive directions of each of X -axis and Y -axis, then the angle that the line makes with the positive direction of the Z axis is
MEDIUM
If the origin and the points P( 2,3,4 ),Q( 1,2,3 ) and R( x,y,z ) are co-planar then
EASY
If vector r with direction cosine l,m,n is equally inclined to the co-ordinate axes, then the total number of such vectors is
MEDIUM
ABC is a triangle in a plane with vertices A2, 3, 5, B-1, 3, 2 and Cλ, 5, μ . If the median through A is equally inclined to the coordinate axes, then the value of λ3+μ3+5 is
EASY
L and M are two points with position vectors 2 a b and a +2 b respectively. The position vector of the point N which divides the line segment LM in the ratio 2:1 externally is
MEDIUM
If a point R4,y,z lies on the line segment joining the points P2,-3,4  and Q8,0,10, then the distance of R from the origin is
MEDIUM
What is the angle subtended by an edge of a regular tetrahedron at its center?
EASY
If a unit vector a makes angles π3 with i^, π4 with j^ and θ0,π with k^, then a value of θ is:
EASY
A line makes angles α, β, γ with the coordinate axes. If α+β=π2, then cosα+cosβ+cosγ2 is equal to
EASY
XY-plane divides the line joining the points A(2, 3, 5) and B(1, 2, 3) in the ratio
EASY
ABC has vertices at A2, 3, 5, B(-1, 3, 2) and Cλ, 5, μ. If the median through A is equally inclined to the axes, then the values of λ and μ respectively are
MEDIUM
The plane which bisects the line segment joining the points -3, -3, 4 and 3, 7, 6 at right angles, passes through which one of the following points?
EASY
A variable plane passes through a fixed point 3, 2, 1 and meets x, y and z-axes at A, B & C respectively. A plane is drawn parallel to the yz plane through A, a second plane is drawn parallel to the zx- plane through B and a third plane is drawn parallel to the xy- plane through C. Then the locus of the point of intersection of these three planes, is