- #1

- 457

- 0

What do i do. I need help some serious help with this one.

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- Thread starter afcwestwarrior
- Start date

- #1

- 457

- 0

What do i do. I need help some serious help with this one.

- #2

- 457

- 0

what equation do i use

- #3

- 62

- 0

Pythagoras Theorem A^2+B^2=C^2

- #4

- 457

- 0

then i square root 4225 and i get 65 which is the answer in my book, thanks man if this is the right way to do it

- #5

- 62

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NO you have to do the dy/dx to get the incresing speed!

- #6

- 457

- 0

whats the dy/dx is it 2

- #7

- 457

- 0

ok so i have to find the derivative of he P.T which is 2c=2a+2b

- #8

- 62

- 0

but you have to calculate how much have they both travel in 2 hour and put into the equation and solve!

- #9

- 457

- 0

ok so is this what it will look like c=2*60+2*25

- #10

- 62

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dy/dx is the speed a b and c is distance~!

- #11

- 457

- 0

so in 2 hours 60mi/h is 120 mi and 25 is 50 mi

- #12

- 62

- 0

- #13

- 457

- 0

so the distance is 170 mi

- #14

- 457

- 0

so what would it look like

- #15

- 457

- 0

would it look like this 2c=2*60+2*25

2c=170

c=170/2

2c=170

c=170/2

- #16

HallsofIvy

Science Advisor

Homework Helper

- 41,833

- 963

As yaho8888 alrready told you, you need to differentiate both sides of c

(And c, the distance between the cars after 2 hours, is NOT 170 miles.

- #17

- 62

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you have to solve for dc/dt~!

The question ask you for speed! dx/dy means speed remember that.

dc/dt(2c) = da/dt(2a)+db/dt(2b)

first solve the distance between a and b in two hours use Pythagoras Theorem.

(2*60mi/hr)^2+(2*25mi/hr)^2= c^2

if you calculate that out c = 130miles

you found the c plug into the equation~!

dc/dt(2*130miles) = (60mi/hr)*(2*120mi) +(25mi/hr)*(2*50mi)

then just solve for dc/dt~!

which is 65mile/hr!

- #18

- 457

- 0

oh, i thought i had to differentiate the pythagorean theorem.

- #19

- 457

- 0

thanks man, how come when i plug in 25^+60^2=4225 square root of 4225 i get the same answer

- #20

- 62

- 0

Man you have no Idea what calculus is!

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