JEE MainMathematicsParabola
Let a focal chord of the parabola y^2 = 16x have a length of 25 . The area of the triangle formed by this focal chord and the vertex of the parabola is
Correct answer
40
Step-by-step solution
The equation of the parabola is y^2 = 16x , so a = 4 . The length of a focal chord inclined at an angle to the axis is given by l = 4a cosec ^2 . Given l = 25 , we have: 16 cosec ^2 = 25 cosec ^2 = 25 16 = 4 5 The perpendicular distance d from the vertex (0,0) to the focal chord is d = a . d = 4 4 5 = 16 5 The area of the triangle formed by the focal chord and the vertex is: Area = 1 2 base height = 1 2 l d Area = 1 2 25 16 5 = 40 Answer: 40