A beam rest against a wall forming a 55 degree angle with the floor

is the same as 1/cos (x) they tell you the angle x is 55 degrees I would do y = 9

9/cos (x) for x=55º y = 9/cos (55 deg) you could type this into google's input window

: 9/cos (55 deg) = Be sure to put in the deg or google will think the 55 is in radians