## agillogly 3 years ago Help!

1. goformit100

ya say

2. agillogly

3. goformit100

solve it by cosine rule

4. agillogly

I don't know how to.

5. kr7210

|dw:1339191253421:dw|

6. kr7210

use it

7. agillogly

How? I don't have all the measurements.

8. alanli123

You don't need all the measurements

9. alanli123

One sec

10. alanli123

|dw:1339195102769:dw|

11. alanli123

You know what b, c, and angle theta are. all you have to do is plug it in and solve for a

12. agillogly

Okay

13. agillogly

I got 130.9 and that isn't and option.

14. alanli123

one sec

15. alanli123

16. agillogly

I just tried to plug everything in like you said. 7^2+9^2-2(7)cos(117). I got 136.35. I did something wrong the first time. But its obviously still wrong.

17. alanli123

Ok here's where you are wrong. It's 7^2+9^2-2ab cos 117. Can you see where you went wrong? (hint: you're missing b)

18. alanli123

You did -2(7), the correct term should be -2(7)(9) because it is -2ab

19. agillogly

Okay. I thought I forgot a number. Ill try it again.

20. agillogly

187.20?

21. alanli123

Yes!

22. kr7210

|dw:1339192083258:dw|

23. alanli123

You are correct!

24. kr7210

25. alanli123

26. agillogly

I picked 187.2 and it said the correct answer is 13.68.

27. kr7210