Find the distance from point Q to the ground (line T) when the angle created By the left side of the seating board and the central support is 80° .
Draw QM intersecting RT at M and parallel to T
Then.....triangle RQM is right with angle RQM = 10°
Then we have that
sin (RQM) = RM / QR
sin (10°) = RM / QR
QR sin (10°) = RM
Then....the height of Q above the ground is given by :
RT - RM =
RT - QRsin (10° )