## tw101 one year ago Using the law of cosines, in triangle RST, if r=14yd, s=9yd, t=6yd, find m<S

1. campbell_st

do you know the formula for the law of cosines when finding an angle...?

2. tw101

c^2=a^2+b^2/2abcos(

3. tw101

whoops messed up

4. tw101

c=a2+b2﹣2abcosγ

5. anonymous

got picture?

6. tw101

No, sorry. Thats all it gave me.:(

7. campbell_st

close,this is what you need $\cos(S) = \frac{r^2 + t^2 - s^2}{2 \times r \times s}$ plug the values in and calculate, the answer is a decimal less than 1. when you get the answer, you then then $\\S = cos^{-1}(answer)$

8. tw101

okay. Ill plug it into my calculator. one sec.

9. campbell_st

oops correction it should read $\cos(S) = \frac{r^2 + t^2 -s^2}{2 \times r \times t}$

10. tw101

okay i got 151/168

11. tw101

or .90

12. campbell_st

great so the next step is $S = \cos^{-1}(\frac{151}{168})$

13. tw101

26

14. campbell_st

that was my solution

15. tw101

Thank you so much!