KCET2009MathematicsParabola
The angle between the tangents drawn to the parabola y²=12 x from the point (-3,2) is
Options
- A90^
- B60^
- C30^
- D45^
Correct answer
A. 90^
Step-by-step solution
Let S=y²-12 x Equation of pair of tangents is gathered SS ₁= T ² ( y ²-12 x ) [(2)²-12(-3) ] =[ y (2)-6( x -3)]² ( y ²-12 x )(40)=4( y -3 x +9)² 10 y ²-120 x = y ²+9 x ²+81-6 yx -54 x +18 y 9 x ²-9 y ²-6 xy +66 x +18 y +81=0 Here, a =9, ~b =-9 a + b =0 gathered Hence, angle between tangents is 90^ .