Question 1106004
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<pre>
Your angle (I will call it "angle A") is concluded between the sides of 18 m (road) and 12 m (fence).


This angle is opposite to the side of 10 m.


Use the Cosine Law:


10^2 = 18^2 + 12^2 - 2*18*12*cos(A),


which gives  cos(A) = {{{(18^2 + 12^2 -10^2)/(2*18*12)}}} = 0.8519.


Then  < A = arccos(0.8519) = 0.55 radians = 31.6 degrees (approximately).
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On cosine law, &nbsp;see the lessons

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/Trigonometry-basics/Proof-of-the-Law-of-Cosines-revisited.lesson>Proof of the Law of Cosines revisited</A>

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/Trigonometry-basics/Solve-triangles-using-Law-of-Cosines.lesson>Solve triangles using Law of Cosines</A>

in this site.