#### Answer

a) for all (x,y)
b) for all (x,y) except (0,0)

#### Work Step by Step

a) We know that $\sin t$ is defined for all real numbers. Thus, for all $(x,y)$
b) $\ln t$ is defined for positive real numbers except for $(0,0)$.

Published by
Pearson

ISBN 10:
0321999584

ISBN 13:
978-0-32199-958-0

a) for all (x,y)
b) for all (x,y) except (0,0)

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