Parabola 2 Question 31

10. The angle between the tangents drawn from the point (1,4) to the parabola y2=4x is

(2004, 1M)

(a) π6

(b) π4

(c) π3

(d) π2

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Answer:

Correct Answer: 10. c14,12c5

Solution:

  1. We know, tangent to y2=4ax is y=mx+am.

Tangent to y2=4x is y=mx+1m

Since, tangent passes through (1,4).

4=m+1mm24m+1=0( whose roots are m1 and m2)m1+m2=4 and m1m2=1 and |m1m2|=(m1+m2)24m1m2=12=23

Thus, angle between tangents

tanθ=|m2m11+m1m2|=|231+1|=3θ=π3



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