If the distance between the two boats is then
For minimum differentiate this (no need to take the square root), and equate the result to zero.
The World Problem:
At 9:30am, one ship was 65 miles due east from a second ship. If the first ship sailed west at 20 miles per hour and the second ship sailed southeast at 30 miles per hour, when were they closest together?
What I Have So Far:
1st ship coordinates: (0,0)
2nd ship coordinates: (-65,0)
Letting time be 't' in hours since 9:30am :
1st ship coordinates: (-20t,0)
2nd ship coordinates: ( )
Not sure where to go where to go from here... Can anyone help me out?