A math problem is urgently needed! There will be prizes for important questions in the mid-term exam tomorrow! The process should be comprehensive in order to divide the points. The above parts are supplemented. Make AD midpoint e and connect EM.

Because m and e are the midpoint of AD and AB respectively, DE = BM = AE = AM.

Because AE = am again? A = 90 degrees So what? AEM = 45 degrees. So what? DEM=？ CBM = 135 degrees

Because? ADM+？ Dma = 90 degrees again? DMA+？ NMB = 90 degrees. So what? ADM=？ The National Maritime Board.

Then prove the triangle DAE congruent triangles NMB.

Finally, MD = Mn is obtained.

The process is a little less, but the general method is like this.