[考古] 臺聯大今年一題

[tn00330905 (普萊亞)]

The coordinates of a particle in the xy-plane are differentiable functions of

time t with dx/dt= -1 m/sec and dy/dt= -5 m/sec. How fast is particle's

distance form the origin changing as it pass through the point (5, 12)?

懇請解答<(_ _)>

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推 powernba:總覺得是不是少條件了?
推 GARY0108:轉學版有人給答案了d/dt (x^2+y^2)^1/2
→ GARY0108:然後代入dx/dt=-1 dy/dt=-5 (x,y)=(5,12)
→ GARY0108:可以得到答案為-5