Solution :
Let
be the unit vector in the direction parallel to the plane and let
be the component of F in the direction of
and
be the component normal to
.
Since, 


Therefore, 
From figure,

We know that the direction of
is opposite of the direction of
, so we have



The unit vector in the direction normal to the plane,
has components :


Therefore, 
From figure,

∴ 

Therefore,


The answer is D.
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A quadratic function is one of the form f(x) = ax2 + bx + c, where a, b, and c are numbers with a not equal to zero. The graph of a quadratic function is a curve called a parabola. ... A parabola intersects its axis of symmetry at a point called the vertex of the parabola. You know that two points determine a line.