Question 1205897
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Sides of a triangle are 8, 11, 13. find the largest angle of the triangle
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<pre>
The largest angle is opposite to the longest side, which is 13 units long.


Write the cosine law equation

    13^2 = 8^2 + 11^2 - 2cos(a)*8*11,

where "a" is the angle between the sides 8 and 11 units long.


You get then

    cos(a) = {{{(8^2 + 11^2 - 13^2)/(2*8*11)}}} = {{{16/(16*11)}}} = {{{1/11}}}.


Hence,  a = {{{arccos(1/11)}}} = 1.479761549 radians = 84.7840914 degrees.    <U>ANSWER</U>
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Solved.