First, the height of the ramp is half of its shorter edge, i.e. 2.2/2 = 1.1 m.



Second, the length of the diagonal of the ramp is   = .



Third,  

    sin(a) =  = 0.216,     (1)

where "a" is the angle under the question.



Now use your calculator to find "a" from equation (1), your answer.