# Thread: Help on precalculus plane vector problem

1. ## Help on precalculus plane vector problem

A plane travels 170 miles at a heading of N 41 degrees W. It then changes direction and travels 165 miles at a heading of N 70 degrees W. How far is the plane from its original position?

2. Originally Posted by lbj2322
A plane travels 170 miles at a heading of N 41 degrees W. It then changes direction and travels 165 miles at a heading of N 70 degrees W. How far is the plane from its original position?
Hint: Draw a picture.

You should end up with a triangle with $a = 165\textrm{miles}$ and $b = 170\textrm{miles}$, and the angle between them $C = 151^{\circ}$.

Use the cosine rule to find $c$

$c^2 = a^2 + b^2 - 2bc\cos{C}$.

3. wouldnt the angle between them have to be obtuse?

4. angle is actually 151 but thanks for giving me an idea of what to do

5. Originally Posted by lbj2322
angle is actually 151 but thanks for giving me an idea of what to do
Yes it is sorry, that was a typo... Fixed.