Question

See attachment, please

Answer 1

\[\huge \iint\limits_D f(x,y)dA=\iint\limits_Df(x,y)dxdy\]

Answer 2

\[\huge \iint\limits_Df(r\cos \theta \ , \ r\sin \theta)rdrd\theta\]

Answer 3

Just forgot an extra r is all :)

Answer 4

ya. thanks a lot

Answer 5

one more question, how to put those symbol in? it looks good

Answer 6

Double integral is
\iint

Answer 7

double integral with a D underneath is
\int\limits_{D}

Answer 8

thanks

Answer 9

\iint, sorry

Answer 10

\iint\limits_{D}

Answer 11

ha , the last one is the right one, right?

Answer 12

last one is right

Answer 13

thank you very much