hard calculus applications question! (1 Viewer)

[Porcia]

Fitzpatrick 25(a)

18. TWO straight toads meet at an angle of 60 degrees. A starts from the intersection and travels along one road at 40km/hr. One hour later B starts from the intersection and travels along the other road at 50km/hr. At what rate is the distance between them changing three hours after A starts?

appreciated! thanks

 

[SoulSearcher]

Pretty much correct, only problem is in this line:

dC/dt = 10(42t -30)/rt(21t² - 30t + 25)

You forgot the 2 in the denominator when it was being derived.
dC/dt = 10(42t-30)/2rt(21t² - 30t + 25)
= 5(42t-30)/rt(21t² - 30t + 25)

Sub the values in that one and you should get the right answer.