## BloomLocke367 one year ago last question for this unit.

1. BloomLocke367

@geerky42 In triangle XYZ, XY=13. YZ=20, and XZ=25. What is the measure of angle Z?

2. BloomLocke367

|dw:1433265703262:dw|

3. geerky42

Use law of cosines here.

4. Nnesha

law of cosine? it's not a right triangle c^2 = a^2 + b^2 -2abcosC

5. BloomLocke367

soooo which is what part?

6. Nnesha

|dw:1433265930207:dw|

7. Nnesha

|dw:1433265972665:dw| opposite sides

8. BloomLocke367

so 169=400+625-2(20)(25)cos(C)

9. Nnesha

yep looks right

10. BloomLocke367

169=1025-1000cosC

11. Nnesha

yep right

12. BloomLocke367

and now I have to isolate C, right?

13. Nnesha

yep right cos C

14. BloomLocke367

soooo 1000cosC+169=1025 1000cosC=846 cosC=846/1000 C=arccos(846/1000), right?

15. Nnesha

mhm first you have to subtract 1025

16. Nnesha

well nvm it's 856 right ?

17. BloomLocke367

I did it a different way, but does it end up being the same?

18. Nnesha

1025 - 169 = ?

19. BloomLocke367

856

20. Nnesha

Yep right it's 856/1000

21. BloomLocke367

so I got 32.22

22. BloomLocke367

that's not an option.... O.O

23. Nnesha

i didn't get 32

24. Nnesha

tryy again

25. Nnesha

it's not 846

26. Nnesha

$$\color{blue}{\text{Originally Posted by}}$$ @BloomLocke367 soooo 1000cosC+169=1025 1000cosC=846 cosC=846/1000 C=arccos(846/1000), right? $$\color{blue}{\text{End of Quote}}$$ 1025-169 = 856 not 846

27. BloomLocke367

dang ittttt I keep doing that today.. writing stuff down wrong.

28. BloomLocke367

sorry.

29. Nnesha

it's okay

30. BloomLocke367

I got ~31

31. Nnesha

yep

32. BloomLocke367

Can you check something for me? just check that my reasoning is correct?

33. Nnesha

okie

34. BloomLocke367

nevermind. I got it, don't worry about it

35. Nnesha

mhmm idunno area stuff but 30-6-90 triangle ....make sense that's right i guess looks right

36. BloomLocke367

thanks