Question

Question about partial differentiation:
f(x,y)=(e^x)(siny)
find values of x and y when fx=0 and fy=0 simultaneously

Answer 1

what u got as fx=0 ?

Answer 2

(e^x)(siny)

Answer 3

e^x can't be 0, so sin y=0

Answer 4

fy=(e^x)(cosy)

Answer 5

similarly, for fy=0, u get cos y=0

Answer 6

what about if i divide fx and fy so that e^x is eliminated and left tany=0?

Answer 7

tan y =0 will imply that sin y=0 and cos y NOT =0
which is not true.

Answer 8

thats because you cannot divide by 0(e^x cos x=0)

Answer 9

got that ?

Answer 10

instead of dividing, why don't u multiply ?
and use sin 2x = 2 sin x cos x

Answer 11

oh,ok.I m trying nw,thx ^^