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Questions  

The minimum area of the triangle formed by the tangent  to x2a2+y2b2=1 and the coordinate axes is 

a
ab sq. units
b
a2+b22 sq. units
c
(a+b)22 sq. units
d
a2+ab+b23 sq. units

detailed solution

Correct option is A

Any tangent to the ellipsex2a2+y2b2=1  at P(acos⁡θ,bsin⁡θ) is given byxcos⁡θa+ysin⁡θb=1 It meets the coordinate  axes at A(asec⁡θ,0) and B(0,bcosec⁡θ) . Therefore,  Area of ΔOAB=12×asec⁡θ×bcosec⁡θ or  Δ=absin⁡2θ For area to be minimum, sin⁡2θ should be maximum and we  know that the maximum value of sin⁡2θ is 1 . Therefore, Δmax=ab

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