Question 148137
First let's draw a picture of the problem:


<img src="http://i150.photobucket.com/albums/s91/jim_thompson5910/13.jpg" alt="Photobucket - Video and Image Hosting">



From the picture, we can see that the opposite side is "x" and the adjacent side is 50. So let's use the tangent function to find the unknown length 


Remember, the tangent function is {{{tan(a)=opposite/adjacent}}} where "a" is the angle



{{{tan(a)=opposite/adjacent}}} Start with the given equation.



{{{tan(76.8)=x/50}}} Plug in {{{a=76.8}}} and the given lengths of the legs of the triangles.



{{{50tan(76.8)=x}}} Multiply both sides by 50.



{{{50(4.264)=x}}} Take the tangent of 76.8 to get 4.264 (note: make sure that you are in "degree" mode)



{{{213.2=x}}} Multiply



So the answer is approximately {{{x=213.2}}} which means that the width of the river is about 213.2 meters