how do you work out a trig problem if the denomonator is unkown

Example:   sin(Angle)   =  opposite / hypotenuse

If the   angle = 40°  and   the opposite side = 10   and   the hypotenuse is unknown:

--->   sin(40°)  =  10/x

--->   x · sin(40°)  =  10                  (multiply both sides by x)

--->   x  =  10 / sin(40°)                 (divide both sides by sin(40°))

--->   x  =  15.6