Re: [微分] 102台聯大

作者: Honor1984 (希望願望成真)   2014-07-02 17:37:45
※ 引述《nsr1290 (許噴)》之銘言:
: The coordinates of a particle in the xy-plane are differential
: function of time t with dx/dt=-1 m/sec dy/dt=-5 m/sec.
: How fast is particle's distance form the origin changing as it passes
from
: through the point(5 , 12)?
: Thank you!
R = √[x^2 + y^2]
x_0 = 5
y_0 = 12
dR/dt |
(5, 12)
= (xx' + yy')/R
= (-5 - 60)/13
= -5 (m/sec)

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