Question
The locus of the middle points of chords of the parabola $${y^2} = 8x$$ drawn through the vertex is a parabola whose :
A.
focus is $$\left( {2,\,0} \right)$$
B.
latus rectum $$ = 8$$
C.
focus is $$\left( {0,\,2} \right)$$
D.
latus rectum $$ = 4$$
Answer :
latus rectum $$ = 4$$
Solution :
If the middle point of a chord is $$\left( {\alpha ,\,\beta } \right)$$ then $$\alpha = \frac{{2{t^2} + 0}}{2},\,\,\beta = \frac{{4t + 0}}{2}$$
Eliminating $$t,\,\alpha = {\left( {\frac{\beta }{2}} \right)^2}.$$ So, the locus is $${y^2} = 4x.$$