For a square membrane with fixed edges, sets the mode shape and the cosine factor reverses its displacement in time. Wherever a sine factor is zero, the membrane stays still.对于边缘固定的方形膜， 决定振型，余弦因子控制位移随时间正负交替。任一正弦因子为零的位置，始终保持静止。
The gold line marks ; the cyan lines mark and . These nodal lines separate six regions that oscillate with alternating signs.金线标出 ，青线标出 和 。这些节线分出六个区域，相邻区域的位移符号相反。