计算变螺距螺杆虚线方程及其圆柱面展开线方程。输入初始螺距、终止螺距、螺线直径、螺杆长度，便可得到螺线圈数，螺线方程、螺线长度、展开线方程及其长度-Calculation equation and the variable pitch cylindrical screw dashed line equation to start. Enter the initial pitch, the termination pitch, spiral diameter, screw length, will be entitled to the number of spiral coils, spiral equation, spiral length, start and length of the line equation