T is a point on the tangent to a parabola y2= 4ax at its point P. TL a...
To understand why option 'C' is the correct answer, let's analyze the given situation step by step.
1. Tangent to the Parabola:
Consider a point T on the tangent to the parabola y^2 = 4ax. Let's denote the coordinates of point T as (x1, y1).
2. Point P on the Parabola:
Since T lies on the tangent, it is also the point of contact of the tangent with the parabola. Therefore, the coordinates of point P can be written as (x1, y1^2/4a).
3. Focal Radius SP:
The focal radius SP is the line segment joining the focus S (0, a) and point P (x1, y1^2/4a). Let's calculate the slope of this line segment.
- Slope of SP = (y1^2/4a - a)/(x1 - 0)
= (y1^2 - 4a^2)/(4ax1)
4. Perpendicular TL:
Let TL be the perpendicular from point T to the focal radius SP. Since TL is perpendicular to SP, the product of their slopes will be -1.
- Slope of TL * Slope of SP = -1
- Slope of TL * (y1^2 - 4a^2)/(4ax1) = -1
- Slope of TL = -4ax1/(y1^2 - 4a^2)
5. Directrix of the Parabola:
The equation of the directrix of the parabola y^2 = 4ax is given by x = -a.
6. Perpendicular TN:
Let TN be the perpendicular from point T to the directrix of the parabola. Since TN is perpendicular to the directrix, its slope will be zero.
- Slope of TN = 0
Now, let's compare the lengths of SL and TN.
7. Length of SL:
SL is the distance between the points S (0, a) and L (x1, -a). Using the distance formula, we can calculate the length of SL.
- Length of SL = √[(x1 - 0)^2 + (-a - a)^2]
= √[x1^2 + 4a^2]
8. Length of TN:
TN is the distance between the points T (x1, y1) and N (-a, y1). Using the distance formula, we can calculate the length of TN.
- Length of TN = √[(x1 + a)^2 + (y1 - y1)^2]
= √[(x1 + a)^2]
Now, let's compare the lengths of SL and TN.
9. Comparing Lengths:
We need to compare SL and TN, so let's square both the lengths and simplify the expression.
- (Length of SL)^2 = x1^2 + 4a^2
- (Length of TN)^2 = (x1 + a)^2
10. Simplifying the Expression:
Since we need to compare 2(SL) and 3(TN), let's calculate the values of 2(SL)^2 and 3(TN)^2.
- 2(SL)^2 = 2(x1^2 +
T is a point on the tangent to a parabola y2= 4ax at its point P. TL a...
D
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