If f(x,y)=excos(y)f(x,y) = e^x \cos(y)f(x,y)=excos(y), find the second-order partial derivative fxxf_{xx}fxx.
excos(y)e^x \cos(y)excos(y)
−excos(y)-e^x \cos(y)−excos(y)
−exsin(y)-e^x \sin(y)−exsin(y)
exsin(y)e^x \sin(y)exsin(y)