## warpedkitten one year ago Zack, Rachel, and Maddie are unraveling a huge ball of yarn to see how long it is. As they move away from each other, they form a triangle. The distance from Zack to Rachel is 3 meters. The distance from Rachel to Maddie is 2.5 meters. The distance from Maddie to Zack is 4 meters. Find the measures of the three angles in the triangle.

1. anonymous

looks like a law of cosines problem to me

2. warpedkitten

It is, but I'm not understanding it. I've done similar problems and it seems like every time I try, I don't get any of the answer choices.

3. anonymous

lets agree on this labelling, i will let you fill in the names etc

4. anonymous

|dw:1433387769343:dw|

5. anonymous

B is opposite the largest side, so it is the largest angle, we can find that first

6. anonymous

$b^2=a^2+c^2-2ac\cos(B)$ but we want the angle so $\cos(B)=\frac{a^2+c^2-b^2}{2ac}$

7. anonymous

filling in the numbers we get $\cos(B)=\frac{3^2+2.5^2-4^2}{2\times 3\times 2.5}$

8. anonymous

take the arccosine to find B

9. princeevee

satellite can you help me?

10. anonymous

i must have made some mistake here

11. anonymous

oh, no i didn't here use the calculator http://www.wolframalpha.com/input/?i=arccos%28%283^2%2B2.5^2-4^2%29%2F%282*3*2.5%29%29

12. anonymous

looks like the largest angle is $$92.87^\circ$$ find the next one of your choice using the law of sines

13. warpedkitten

I've got it now, thank you!