What did I do wrong in calculating the x-component of net displacement?

[Joe91090]

What did I do Wrong ??

Homework Statement

A car travels 2.14km in the x direction then turns left 71.6 degrees to the original direction and travels an additional distance of 2.58km. calculate the x component of the cars net displacement.

Homework Equations

law of cosines

The Attempt at a Solution

plugged knowns into law of cosines equations got 2.78. what did I do wrong ??

 

[gabbagabbahey]

Draw a picture, you should have a right triangle. There is no need for the law of cosines.

 

[Joe91090]

Ive drawn several pictures does it just look like a right triangle ?

 

[gabbagabbahey]

Draw a line downwards from the final position to the x-axis...now do you see the right triangle?

 

[Joe91090]

is your first movemment to the east ?

 

[gabbagabbahey]

Yes. Isn't yours?

 

[Joe91090]

yes then your 71.6 degrees left so does yours look acute or obtuse ?

 

[Joe91090]

well if your saying its a right angle it must be acute. I am still not sure its a right angle

 

[gabbagabbahey]

Perhaps this will clarify things:

http://img15.imageshack.us/img15/8913/42550387.th.jpg

 

[Joe91090]

so the answer would be the displacement from (0,0) to the tip of the other vector ?

 

[gabbagabbahey]

so the answer would be the displacement from (0,0) to the tip of the other vector ?

No, the total x-component is 2.14km plus the x-component of the angled vector.

http://img15.imageshack.us/img15/5861/39469841.jpg