We will have the following:
First, using the law of cosines we find the lenght of the missing side:
c = (a^2 + b^2 - 2a*b*cos(C))^(1/2)
That is:
c = (122^2 + 74^2 - 2(122)(77)cos(58))^(1/2)
c = 103.8834817
c is approximately 103.9 meters in legth.
Now, using the law of sines, we calculate the angle of inclination of this segment:
103.8834817 / sin(58) = 122.0 / sin(x)
so
sin(x) = 122.0 * sin(58) / 103.8834817
Then
x = Arcsin(122.0 * sin(58) / 103.8834817)
Finally we get that the measure