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avatar+105 

so a triangle is 180 degress. i have a word problem and i can only seem to get as high as 176 degrees. 

Problem 

suppose you have a triangle where A=47(degrees), side b=7.00, and side c=3.59. Use cosine law to find side a, angle B and angle C. 


my answers so far are..
a=5.25
B=99
C=30.34

=176.  

any help would be greatly appricated!!! 

 Jun 18, 2014

Best Answer 

 #1
avatar+26396 
+11

Hi Strider,

α=47\ensuremathb=7c=3.59side a?angle β ? and angle γ ?

a:

a2=b2+c22bccos(47\ensuremath)a2=72+3.592273.59cos(47\ensuremath)a2=27.6108624233a=5.25460392639

β:

b2=a2+c22accos(β)cos(β)=a2+c2b22accos(β)=0.22532402766β=103.021932880\ensuremath

γ:

c2=a2+b22abcos(γ)cos(γ)=a2+b2c22abcos(γ)=0.86621674081γ=29.9780671201\ensuremath

α+β+γ=47\ensuremath+103.021932880\ensuremath+29.9780671201\ensuremath=180.000000000\ensuremath

 Jun 18, 2014
 #1
avatar+26396 
+11
Best Answer

Hi Strider,

α=47\ensuremathb=7c=3.59side a?angle β ? and angle γ ?

a:

a2=b2+c22bccos(47\ensuremath)a2=72+3.592273.59cos(47\ensuremath)a2=27.6108624233a=5.25460392639

β:

b2=a2+c22accos(β)cos(β)=a2+c2b22accos(β)=0.22532402766β=103.021932880\ensuremath

γ:

c2=a2+b22abcos(γ)cos(γ)=a2+b2c22abcos(γ)=0.86621674081γ=29.9780671201\ensuremath

α+β+γ=47\ensuremath+103.021932880\ensuremath+29.9780671201\ensuremath=180.000000000\ensuremath

heureka Jun 18, 2014
 #2
avatar+130458 
0

..........delete..........

 Jun 18, 2014
 #3
avatar+105 
0

Is something wrong CPhill? and thanks heureka!

 Jun 18, 2014
 #4
avatar+130458 
0

No, Strider, I was in the middle of working your problem when I noticed that heureka had provided an answer....and as I couldn't top "perfection," there was no need to try to duplicate it, either!!.....

 

 Jun 18, 2014
 #5
avatar+105 
0

Ah, alright 

 Jun 18, 2014

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