JEE Main 20204 Sep, Morning shiftMathematicsMediumLimit, Continuity and Differentiability420× since 2002If (a+2bcosx)(a−2bcosy)=a2−b2\left( {a + \sqrt 2 b\cos x} \right)\left( {a - \sqrt 2 b\cos y} \right) = {a^2} - {b^2}(a+2bcosx)(a−2bcosy)=a2−b2 where a > b > 0, then dxdy at(π4,π4){{dx} \over {dy}}\,\,at\left( {{\pi \over 4},{\pi \over 4}} \right)dydxat(4π,4π) is :AOption A. a−2ba+2b{{a - 2b} \over {a + 2b}}a+2ba−2bBOption B. a−ba+b{{a - b} \over {a + b}}a+ba−bCOption C. a+ba−b{{a + b} \over {a - b}}a−ba+bDOption D. 2a+b2a−b{{2a + b} \over {2a - b}}2a−b2a+bCheckSkip · show solution
