Let T1 and T2 be two distinct common tangents to the ellipse and the parabola . Suppose that the tangent T1 touches P and E at the points A1 and A2, respectively, and the tangent T2 touches P and E at the points A4 and A3, respectively. Then which of the following statements is/are true?
Correct Answer :
The area of the quadrilateral A1A2A3A4 is 35 square units
The tangents T1 and T2 meet the x-axis at the point (-3, 0)
Solution :
The correct options are:
• The area of the quadrilateral A1A2A3A4 is 35 square units
• The tangents T1 and T2 meet the x-axis at the point (-3, 0)
Let us analyze the given curves step-by-step and find their common tangents and points of contact.
Step 1: Equation of Common Tangents
The equation of the given parabola is:
Here, .
Any tangent to the parabola with slope is given by:
Or in standard form:
The equation of the given ellipse is:
Here, and .
For the line to be tangent to the ellipse, the condition of tangency must be satisfied:
Multiplying both sides by :
Factoring the quadratic equation in :
Since must be real and positive, we get .
Therefore, the two common tangents are:
For :
For :
Step 2: Intersection of Tangents with the x-axis
Setting in both tangent equations:
For :
For :
Thus, both tangents and meet the x-axis at the point (-3, 0).
Step 3: Finding the Points of Contact
For a parabola , the point of contact for a tangent with slope is .
• For (), the point of contact on is .
• For (), the point of contact on is .
For an ellipse , the point of contact for a tangent line is given by .
• For (), the point of contact on is .
• For (), the point of contact on is .
Step 4: Area of Quadrilateral A1A2A3A4
The four vertices are:
, , ,
Since the shape is an isosceles trapezium symmetric about the x-axis, we can calculate its area using the formula for the area of a trapezium:
Parallel side 1 (): length =
Parallel side 2 (): length =
Distance between parallel sides (along x-axis):
Substitute these values into the area formula:
Hence, the area of the quadrilateral A1A2A3A4 is 35 square units and the tangents meet the x-axis at (-3, 0).
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