Q.
If the minimum distance of the point (secα,cosecα) from the circle x2+y2=3 can be expressed as a−b, where a,b∈N, then the value of ab is
1192
213
NTA AbhyasNTA Abhyas 2020Conic Sections
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Answer: 1.5
Solution:
Since, (sec)2α+(cosec)2α−3=(1+(tan)2α)+(1+(cot)2α)−3 =−1+(tanα−cotα)2+2=1+(tanα−cot(α)2)>0
Hence, the point (secα,cosecα) lies outside the circle x2+y2−3=0
Now, the minimum distance =(secα−0)2+(cosecα−0)2−3 =4+(tanα−cotα)2−3 (Minimum is attained, when tanα=cotα ) =2−3≡a−b (Given)
So, a=2,b=3.
Hence, ab=23=1.5