For triangles that has a perpendicular side, or right triangles, we could use the trigonometric functions. The right triangle has three sides: the longest side called hypotenuse (h), opposite side (o) and the adjacent side (a). The opposite and adjacent sides are with respect to the angle. Here, LM is the opposite of angle 60 degrees. So, we use the tangent function where
tan60 = o/a = LM/9√2
LM = 9√2 tan60
LM = 9√6