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Mathematics
Mathematics
Problem
In one concise sentence, explain why
∣
r
(
t
)
∣
|\mathbf r(t)|
∣
r
(
t
)
∣
remains constant for all
t
t
t
if
d
d
t
[
r
(
t
)
⋅
r
(
t
)
]
=
0
\dfrac{d}{dt}[\mathbf r(t)\cdot\mathbf r(t)]=0
d
t
d
[
r
(
t
)
⋅
r
(
t
)]
=
0
on an interval.
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