Law of Cosines - Homework Check?

I've been having problems with the Sin, Cos, and Tan problems we've just received. I think I get them, and it turns out they're wrong. I was wondering if someone could check to make sure I've gotten the right answers: my grade really needs the boost. (answers will be in |x|brackets. %26lt; means angle. d means degrees.)





The Law of Cosine is used for these:


1. j=9.6, l=1.7, %26lt;K=43. find side k. |k=8.4|


2. m=17, n=23, q=25. find %26lt;Q |%26lt;Q=75.7 d|


3. m=23, n=30.1, q=42. find %26lt;Q |%26lt;Q=103.7 d|


4. Find line c, %26lt;A, and %26lt;B


a=6, b=19, %26lt;C=38


|c=14.7, %26lt;A=14 d, %26lt;B= 128 d|


5. Find line c, %26lt;A, and %26lt;B


a=15.5, b=18, and %26lt;C=72


|c=19.8, %26lt;A=48 d, %26lt;B=60 d|





This one can use either Law of Sine or Law of Cosine.


6. Find all the missing sides/angles


%26lt;F=54, f=12.5, g=11


I used Law of Sine and got


|%26lt;G=44 d, %26lt;H= 82 d, h=15.6|





Back to Law of Cos


7. c=76, b=85, %26lt;A=80. Find side a.


|a=104|


8. %26lt;S=43, t=37, u=20. Find side s.


|s=26.2|





That's all there is.


And I will be going to tutoring tomorrow.

Law of Cosines - Homework Check?
1) - correct


2) - correct


3) - correct


4) - I make A slightly closer to 15° (14.51°) and hence B to 127°. Likely just a rounding issue.


5) - correct


6) - I get %26lt;G = 45° (45.4° to 1 d.p.), %26lt;H = 81° and h = 15.2. Did you round off sin 54° to only a couple of decimal places and then use the rounded-off value in your calculations? You should always use 1-2 more significant figures in the intermediate calculations than you want in the final figure.


7) - correct


8) - correct





Looks like you've got it taped! Just don't round your calculations too early and you'll be fine.