The position vector of a point P is →r=x^i+y^j+z^k, when x,y,zϵ N and →a=^i+^j+^k.If→r.→a=10, the number of possible position of P is
36
72
66
¯r.¯a=10 ⇒x+y+z=10,x,y,zϵN no. of solutions = 10−1C3−1=36
If the position vector of a point P is →r=x^i=y^j+z^k, where x, y, zϵ N and projection of →r on →a=^i+^j+^k is 10√3 then number of possible of P is also equal to