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AP EAMCET · Maths · Application of Derivatives

If the straight line xcosα+ysinα=p touches the curve xan+ybn=2 at the point a,b on it and 1a2+1b2=kp2 then k=

  1. A 4
  2. B 5
  3. C 6
  4. D 7
Verified Solution

Answer & Solution

Correct Answer

(A) 4

Step-by-step Solution

Detailed explanation

The line xcosα+ysinα=p is a tangent to xan+ybn=2 at a,b. Differentiating xan+ybn=2, we get nanxn-1+nbnyn-1dydx=0 i.e. dydxa,b=-ba Now equation of tangent at a,b will be y-b=-bax-a⇒ay-ab=-bx+ab ⇒bx+ay=2ab Comparing with xcosα+ysinα=p, we get…