A surveyor's map shows a triangular region divided into two by a North-South boundary line of length y y\,y km. The line y y\,y is perpendicular to the base line of the region. The Western side of the region is bounded by paths of length 7 km and 11 km meeting at an angle of 65∘ 65^\circ\,65∘ at the Northwest vertex. The distance along the base line from the boundary y y\,y to the Eastern vertex is 4 km. The angle at the Eastern vertex is x∘x^\circx∘.
Work out the value of xxx.
Give your answer to 1 decimal place.
