The fact that this method works is related to the SSS method of proving triangles congruent.

Here is the proof diagram.As you work through the following steps, refer to the figure:

**Draw a working line,***l,*with a point*J*on it.**Put your compass point on point**The best way to make sure you’ve opened it to just the right amount is to draw a little arc that passes through*D*and open it to the length of*DE*.*E*. In other words, draw arc (*D*,*DE*).**Being careful not to change the amount of the compass’s opening from Step 2, put the compass point on point**You have now constructed segment*J*and construct arc (*J*,*JK*) intersecting line*l*.*JK*on line*l*that’s congruent to segment*DE.***Construct**a. Arc (*D*,*DF*) b. Arc (*J*,*DF*)**Construct**a. Arc (*E*,*EF*) b. Arc (*K*,*EF*) intersecting arc (*J*,*DF*) at point*L***Draw segments***JL*and*KL*and you’re done.