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Application Of Derivatives

Question
CBSEENMA12035810

Find the equations of the tangent and the normal, to curve 16x2 + 9y2 = 145 at the point (x1,y1) where x1 = 2 and y1 > 0

Solution

16x2 + 9y2 = 145 is the curve and points (x1,y1) where

x1 = 2 and y1 >0

⇒ 16 (2)2 + 9

 16 (2)2 + 9y12 = 145 9y12 = 145 -64 = 81 y12 = 9y1 = ± 3since y1 > 0 y1 =3

So, the required point is (2,3). Now 16x2 + 9y2 = 145, on differentiating w.r.t. x gives

16 (2x) + 18 y dydx = 0dydx = -32 x 18 y = - 16 x 9ySlope of tangent at (2,3) =dydx(2,3) = 16 x 29 x3 = -3227So, equation of tangent is y-y1 = m (x- x1)y -3 = -3227 (x-2)27 y - 81 = 32x + 64323x + 27y = 145 is the equation of tangentslope of normal is -1m = -1-3227 = 2732Equation of normal is y - 3 = 2732 (x-2)32 y- 96 = 27 x -54 27 x - 32 y = 54-96 = -42 27 x -32 + 42 = 

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