We firstly calculate the angle at the bottom left of the triangle(theta)..,
; Angle theta...
tan theta = 9/11
Angle theta = tan^-1(9/11)
; Angle theta = 39.3°
Then height x...we then use the smaller triangle..,
; tan (39.3°) = x/5.5
; x = 5.5 tan(39.3°)
Hence... x = 4.5
