Posted by **Amy** on Sunday, July 24, 2011 at 10:16pm.

Hi I'm reviewing the following solution in my trigonometry text book and I can't figure out how they got their answer. If someone can help explain how they calculated 542.25 for a^2 (nothing I do comes up with that number):

a2=b2+c2-2bcCosA

a2=(16)^2+(11)^2 -2(16)(11)Cos118

a2=542.25

|a2=|542.25

a=23.3

Thank you!

- Math -
**Reiny**, Sunday, July 24, 2011 at 11:14pm
I got exactly that.

a^2= 16^2 + 11^2 - 2(16)(11)cos118°

= 256 + 121 - 352(-.469471562)

= 377 **+** 165.2539898

= 542.253989

a = √542.2539898

= 23.2863

Are you following the order of operation?

- Math -
**Amy**, Monday, July 25, 2011 at 3:12pm
Thank you, I think it was how I was using my calculator. I didn't add brackets, now I got the same too. Very helpful to have that extra confirmation, I can't tell you how long I've been stuck on this question. Thanks a million!

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