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anonymous
 one year ago
I need help with this problem!! It would be much appreciated!!
A street light is mounted at the top of a 15 foottall pole. A man 6ft tall walks away from the pole with the speed of 5ft/s along a straight path. How fast is the tip of his shadow moving away from the pole when he is 40ft from the pole?
anonymous
 one year ago
I need help with this problem!! It would be much appreciated!! A street light is mounted at the top of a 15 foottall pole. A man 6ft tall walks away from the pole with the speed of 5ft/s along a straight path. How fast is the tip of his shadow moving away from the pole when he is 40ft from the pole?

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ganeshie8
 one year ago
Best ResponseYou've already chosen the best response.1dw:1434097565386:dw

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Right, and I think we have to use similar triangles, correct?

ganeshie8
 one year ago
Best ResponseYou've already chosen the best response.1Yes! lets start by labelling stuff

ganeshie8
 one year ago
Best ResponseYou've already chosen the best response.1Say the lamppost is the origin, \(\large y\) represents the position of shadow, \(\large x\) represents the position of man dw:1434098052886:dw

ganeshie8
 one year ago
Best ResponseYou've already chosen the best response.1we're given \( \dfrac{dx}{dt}=5 \) and asked to find \(\dfrac{dy}{dt}\)

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Exactly! I got stuck right here, I don't know what to do from here on

ganeshie8
 one year ago
Best ResponseYou've already chosen the best response.1do you see two similar triangles ?

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Yeah, one with 15 and y, the other with 6 and yx

ganeshie8
 one year ago
Best ResponseYou've already chosen the best response.1dw:1434098406881:dw

ganeshie8
 one year ago
Best ResponseYou've already chosen the best response.1set up a proportion: \[\large \dfrac{15}{y}~~=~~\dfrac{6}{yx}\]

ganeshie8
 one year ago
Best ResponseYou've already chosen the best response.1rearrange a bit and differentiate with respect to \(t\)

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Ohhh okay! Im gonna do that and tell you what i get

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0So is dy/dt = (15(5))/9 ??

ganeshie8
 one year ago
Best ResponseYou've already chosen the best response.1Yes, looks you can cancel 3 and simplify a bit more

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Great!! Thanks so much!! You saved me! :D
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