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Mathematics
Mathematics
Problem
For a smooth curve defined in polar coordinates by
r
=
f
(
θ
)
r=f(\theta)
r
=
f
(
θ
)
, which of the following expressions represents the differential element of arc length
d
s
ds
d
s
in terms of
θ
\theta
θ
? a)
d
s
=
r
d
θ
ds=r\,d\theta
d
s
=
r
d
θ
b)
d
s
=
r
2
+
(
d
r
d
θ
)
2
d
θ
ds=\sqrt{r^{2}+\left(\dfrac{dr}{d\theta}\right)^{2}}\,d\theta
d
s
=
r
2
+
(
d
θ
d
r
)
2
d
θ
c)
d
s
=
r
1
+
(
d
r
d
θ
)
2
d
θ
ds=r\sqrt{1+\left(\dfrac{dr}{d\theta}\right)^{2}}\,d\theta
d
s
=
r
1
+
(
d
θ
d
r
)
2
d
θ
d)
d
s
=
r
2
+
d
r
d
θ
d
θ
ds=\sqrt{r^{2}+\dfrac{dr}{d\theta}}\,d\theta
d
s
=
r
2
+
d
θ
d
r
d
θ
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