Sunday

December 21, 2014

December 21, 2014

Posted by **Furzeen** on Tuesday, November 29, 2011 at 5:58am.

- Math(module 4 Calculus) -
**Reiny**, Tuesday, November 29, 2011 at 7:47amLet the distance from A to his landing place be x

then from there it would be another 5-x miles to his house.

let the distance he rows be d

d^2 = x^2 + 2^2

d = (x^2 + 4)^(1/2)

time for the rowing part = (x^2 + 4)^(1/2) /3

time for the walking part = (5-x)/5

Time = (x^2 + 4)^(1/2) /3 + (5-x)/5

d(Time)/dx = (1/6)(x^2 + 4)^(-1/2) (2x) - 1/5

x/(3√(x^2+4) ) - 1/5

= 0 for a minimum of Time.

x/(3√(x^2+4) ) - 1/5

5x = 3√(x^2 + 4)

25x^2 = 9(x^2+4)

25x^2 = 9x^2 + 36

16x^2 = 36

4x = 6

x = 6/4

sub that into Time = .. and you got it

( I got 1 hour and 32 minutes)

check my arithmetic

- Math(module 4 Calculus) -
**Anonymous**, Friday, December 19, 2014 at 7:10pmyoo

- Math(module 4 Calculus) -
**Anonymous**, Friday, December 19, 2014 at 7:13pmk

**Answer this Question**

**Related Questions**

calculus - A lighthouse is built on an exposed reef, 5.5 miles off-shore. The ...

calculus - A lighthouse is built on an exposed reef, 5.5 miles off-shore. The ...

pre-calc - two lighthouses A and B are positioned along the coast.A ship is ...

pre calc - Lighthouse B is 8 miles west of lighthouse A. A boat leaves A and ...

Math - A LIGHTHOUSE IS 10 MILES NORTHEAST OF A DOCK. A SHIP LEAVES THE DOCK AT ...

Algebra 3 and trig - An ocean liner is 177 miles due west of lighthouse A. ...

Physics - A lighthouse beacon alerts ships to the danger of a rocky coastline. ...

Calculus - A man is in a boat 4 miles off a straight coast. He wants to reach a ...

Math - Lighthouse B is 7 miles west sof lighthouse A. A boat leaves A and sails ...

trigo - a tugboat is 36km due north of lighthouse C. Lighthouse B is directly ...