Vectors:

Asked by  | 1st Jun, 2009, 10:35: PM

Expert Answer:

Let A be the original position of the girl.

AB=4 (westwards)

Let C be to the north of B So

angle CBA=90 degrees

She travels 30 degrees east of North, so she moves at 30 degrees to BC.

Her position after 3  Km is D say.

angle DBA=60 degrees

 

Drop perpendicular from D onto AB meeting it at E say.

now,

 

BE=3cos 60

ED=3sin60

Use AE=AB-EB=4-3cos60

 

now, use pythagoras' thm  for triangle AED, to find AD which is the required distance

Answered by  | 9th Jun, 2009, 08:18: PM

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