The correct option is B π
y cos x+x cos y=π
Differentiate both sides with respect to x, we get
−y sin x+cos x.y′+x(−sin y)y′+cos y
Again differentiate with respect to x
−y"sin x−y cos x+cos x.y"+sinx.y′−sin y.y′−x[cos y.(y′)2+siny.y"]−sin y.y′
Putting x=0,weget−y+y"−2sin y y′=0
y"=y+2y′sin y
Since at x=0,y=π;(y")0=π